Document and Entity Information Document	6 Months Ended
Document and Entity Information Document	Jun. 30, 2019 shares
Document and Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	1-3548
Entity Registrant Name	ALLETE, Inc.
State of Incorporation	MN
Entity Tax Identification Number	41-0418150
Entity Address, Address Line One	30 West Superior Street
Entity Address, City or Town	Duluth
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55802-2093
City Area Code	218
Local Phone Number	279-5000
Title of 12(b) Security	Common Stock, without par value
Trading Symbol	ALE
Name of Exchange	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	51,655,541
Entity Central Index Key	0000066756
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Balance Sheet - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Current Assets [Abstract]
Cash and Cash Equivalents	$ 203.1	$ 69.1
Accounts Receivable (Less Allowance of $1.1 and $1.7)	87.4	144.4
Inventories – Net	78.2	86.7
Prepayments and Other	28.6	34.1
Total Current Assets	397.3	334.3
Property, Plant and Equipment – Net	4,062.9	3,904.4
Regulatory Assets	391.2	389.5
Equity Investments	160.2	161.1
Goodwill and Intangible Assets – Net	1.1	223.3
Other Non-Current Assets	163.8	152.4
Total Assets	5,176.5	5,165.0
Current Liabilities [Abstract]
Accounts Payable	150.4	149.8
Accrued Taxes	41.3	51.4
Accrued Interest	17.7	17.9
Long-Term Debt Due Within One Year	27.7	57.5
Other	59.5	128.5
Total Current Liabilities	296.6	405.1
Long-Term Debt	1,505.9	1,428.5
Deferred Income Taxes	213.5	223.6
Regulatory Liabilities	508.8	512.1
Defined Benefit Pension and Other Postretirement Benefit Plans	163.9	177.3
Other Non-Current Liabilities	282.8	262.6
Total Liabilities	2,971.5	3,009.2
Commitments, Guarantees and Contingencies (Note 7)
Shareholders’ Equity [Abstract]
Common Stock Without Par Value, 80.0 Shares Authorized, 51.7 and 51.5 Shares Issued and Outstanding	1,433.3	1,428.5
Accumulated Other Comprehensive Loss	(26.9)	(27.3)
Retained Earnings	798.6	754.6
Total Shareholders’ Equity	2,205.0	2,155.8
Total Liabilities and Shareholders' Equity	$ 5,176.5	$ 5,165.0

Consolidated Balance Sheet Parentheticals - USD ($) shares in Millions, $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts Receivable [Abstract]
Accounts Receivable, Allowance	$ 1.1	$ 1.7
Common Stock [Abstract]
Common Stock, Par Value	$ 0.00	$ 0.00
Common Stock, Shares Authorized	80.0	80.0
Common Stock, Shares Outstanding	51.7	51.5
Common Stock, Shares Issued	51.7	51.5

Consolidated Statement of Income Consolidated Statement of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating Revenues [Abstract]
Contracts with Customers - Utility	$ 249.8	$ 257.8	$ 532.0	$ 528.0
Contracts with Customers - Non-utility	37.7	80.4	109.8	162.4
Other - Non-utility	2.9	5.9	5.8	11.9
Total Operating Revenue	290.4	344.1	647.6	702.3
Operating Expenses [Abstract]
Fuel, Purchased Power and Gas - Utility	87.9	96.5	197.7	197.4
Transmission Services - Utility	19.2	16.8	37.5	35.2
Cost of Sales - Non-utility	16.5	37.0	47.1	69.9
Operating and Maintenance	66.7	86.8	142.9	173.3
Depreciation and Amortization	50.2	56.1	102.1	101.9
Taxes Other than Income Taxes	13.7	14.4	27.3	30.7
Total Operating Expenses	254.2	307.6	554.6	608.4
Operating Income	36.2	36.5	93.0	93.9
Other Income (Expense) [Abstract]
Interest Expense	(16.3)	(17.1)	(32.8)	(34.0)
Equity Earnings	4.8	4.3	10.4	9.0
Gain on Sale of U.S. Water Services	0.5	0.0	20.6	0.0
Other	4.2	2.2	11.6	4.3
Total Other Income (Expense)	(6.8)	(10.6)	9.8	(20.7)
Income Before Income Taxes	29.4	25.9	102.8	73.2
Income Tax Expense (Benefit)	(4.8)	(5.4)	(1.9)	(9.1)
Net Income	$ 34.2	$ 31.3	$ 104.7	$ 82.3
Earnings Per Share [Abstract]
Basic (Shares)	51.6	51.3	51.6	51.2
Diluted (Shares)	51.7	51.5	51.7	51.4
Basic Earnings Per Share of Common Stock	$ 0.66	$ 0.61	$ 2.03	$ 1.61
Diluted Earnings Per Share of Common Stock	$ 0.66	$ 0.61	$ 2.02	$ 1.60

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Comprehensive Income [Abstract]
Net Income	$ 34.2	$ 31.3	$ 104.7	$ 82.3
Other Comprehensive Income (Loss) [Abstract]
Unrealized Gain (Loss) on Securities Net of Income Tax Expense of $0.1, $–, $0.1 and $–	0.1	0.0	0.2	(0.1)
Defined Benefit Pension and Other Postretirement Benefit Plans Net of Income Tax Expense of $–, 0.1, $0.1 and $0.2	0.2	0.3	0.2	0.7
Total Other Comprehensive Income	0.3	0.3	0.4	0.6
Total Comprehensive Income	$ 34.5	$ 31.6	$ 105.1	$ 82.9

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating Activities [Abstract]
Net Income	$ 104.7	$ 82.3
AFUDC – Equity	(1.3)	(0.5)
Income from Equity Investments – Net of Dividends	(2.2)	(0.4)
Depreciation Expense	100.8	99.2
Amortization of PSAs	(5.8)	(11.9)
Amortization of Other Intangible Assets and Other Assets	3.2	5.0
Deferred Income Tax Benefit	(2.1)	(9.5)
Share-Based and ESOP Compensation Expense	3.3	3.3
Defined Benefit Pension and Postretirement Benefit Expense	2.1	4.3
Payments / Provision for Interim Rate Refund	(40.0)	8.8
Payments / Provision for Tax Reform Refund	(10.3)	6.7
Bad Debt Expense	(0.6)	0.7
Gain on Sale of U.S. Water Services	(20.6)	0.0
Changes in Operating Assets and Liabilities [Abstract]
Accounts Receivable	34.0	1.7
Inventories	(9.5)	(3.2)
Prepayments and Other	3.3	2.8
Accounts Payable	(11.2)	8.1
Other Current Liabilities	(23.9)	(1.3)
Cash Contributions to Defined Benefit Pension Plans	(10.4)	(15.0)
Changes in Regulatory and Other Non-Current Assets	(11.9)	5.8
Changes in Regulatory and Other Non-Current Liabilities	(6.4)	7.5
Cash from Operating Activities	95.2	194.4
Investing Activities [Abstract]
Proceeds from Sale of Available-for-sale Securities	6.0	7.2
Payments for Purchase of Available-for-sale Securities	(5.9)	(9.8)
Payments for Equity Investments	(4.6)	(3.9)
Return of Capital From Equity Investments	8.3	0.0
Proceeds from Sale of U.S. Water Services - Net of Transaction Costs and Cash Retained	264.2	0.0
Additions to Property, Plant and Equipment	(236.0)	(133.4)
Payments for (Proceeds from) Other Investing Activities	14.0	1.4
Cash from (for) Investing Activities	46.0	(138.5)
Financing Activities [Abstract]
Proceeds from Issuance of Common Stock	1.5	10.7
Proceeds from Issuance of Long-term Debt	100.0	72.0
Repayments of Long-Term Debt	(49.8)	(57.9)
Acquisition-Related Contingent Consideration Payments	3.8	0.0
Dividends on Common Stock	(60.7)	(57.4)
Other Financing Activities	(0.8)	(0.6)
Cash for Financing Activities	(13.6)	(33.2)
Change in Cash, Cash Equivalents and Restricted Cash	127.6	22.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 206.6	$ 132.8

Consolidated Statement of Shareholders' Equity Consolidated Statement of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]
Balance, Beginning Balance at Dec. 31, 2017		$ 1,401.4	$ (28.2)	$ 695.5
Consolidated Statement of Shareholders' Equity [Roll Forward]
Common Stock Issued		14.0
Unrealized Gain (Loss) on Debt Securities	$ (0.1)		(0.1)
Defined Benefit Pension and Other Postretirement Plans	0.7		0.7
Net Income				82.3
Common Stock Dividends	57.4			(57.4)
Balance, End of Period at Jun. 30, 2018	$ 2,108.2	1,415.4	(27.6)	720.4
Consolidated Statement of Shareholders' Equity [Roll Forward]
Dividends Per Share of Common Stock	$ 1.12
Balance, Beginning Balance at Mar. 31, 2018		1,407.4	(27.9)	717.8
Consolidated Statement of Shareholders' Equity [Roll Forward]
Common Stock Issued		8.0
Unrealized Gain (Loss) on Debt Securities	$ 0.0		0.0
Defined Benefit Pension and Other Postretirement Plans	0.3		0.3
Net Income				31.3
Common Stock Dividends				(28.7)
Balance, End of Period at Jun. 30, 2018	$ 2,108.2	1,415.4	(27.6)	720.4
Consolidated Statement of Shareholders' Equity [Roll Forward]
Dividends Per Share of Common Stock	$ 0.56
Balance, Beginning Balance at Dec. 31, 2018		1,428.5	(27.3)	754.6
Consolidated Statement of Shareholders' Equity [Roll Forward]
Common Stock Issued		4.8
Unrealized Gain (Loss) on Debt Securities	$ 0.2		0.2
Defined Benefit Pension and Other Postretirement Plans	0.2		0.2
Net Income				104.7
Common Stock Dividends	60.7			(60.7)
Balance, End of Period at Jun. 30, 2019	$ 2,205.0	1,433.3	(26.9)	798.6
Consolidated Statement of Shareholders' Equity [Roll Forward]
Dividends Per Share of Common Stock	$ 1.175
Balance, Beginning Balance at Mar. 31, 2019		1,431.1	(27.2)	794.8
Consolidated Statement of Shareholders' Equity [Roll Forward]
Common Stock Issued		2.2
Unrealized Gain (Loss) on Debt Securities	$ 0.1		0.1
Defined Benefit Pension and Other Postretirement Plans	0.2		0.2
Net Income				34.2
Common Stock Dividends				(30.4)
Balance, End of Period at Jun. 30, 2019	$ 2,205.0	$ 1,433.3	$ (26.9)	$ 798.6
Consolidated Statement of Shareholders' Equity [Roll Forward]
Dividends Per Share of Common Stock	$ 0.5875

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

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+ Details

Operations and Significant Accounting Policies

6 Months Ended

Jun. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Operations and Significant Accounting Policies [Text Block]

OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES

Cash, Cash Equivalents and Restricted Cash. We consider all investments purchased with original maturities of three months or less to be cash equivalents. As of June 30, 2019, restricted cash amounts included in Prepayments and Other on the Consolidated Balance Sheet include collateral deposits required under an ALLETE Clean Energy loan agreement. In prior periods presented, the amounts also include U.S. Water Services' standby letters of credit. The restricted cash amounts included in Other Non-Current Assets represent collateral deposits required under an ALLETE Clean Energy loan agreement and PSAs. In prior periods presented, the amounts also include deposits from a SWL&P customer in aid of future capital expenditures. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheet that aggregate to the amounts presented in the Consolidated Statement of Cash Flows.



Cash, Cash Equivalents and Restricted Cash	June 30, 2019		December 31, 2018		June 30, 2018		December 31, 2017
Millions
Cash and Cash Equivalents		$203.1		$69.1		$121.9		$98.9
Restricted Cash included in Prepayments and Other	0.9		1.3		2.3		2.6
Restricted Cash included in Other Non-Current Assets	2.6		8.6		8.6		8.6
Cash, Cash Equivalents and Restricted Cash on the Consolidated Statement of Cash Flows		$206.6		$79.0		$132.8		$110.1

Inventories – Net. Inventories are stated at the lower of cost or net realizable value. Inventories in our Regulated Operations segment are carried at an average cost or first-in, first-out basis. Inventories in our ALLETE Clean Energy segment and Corporate and Other businesses are carried at an average cost, first-in, first-out or specific identification basis.



Inventories – Net	June 30, 2019		December 31, 2018
Millions
Fuel (a)		$33.4		$26.0
Materials and Supplies	44.8		44.2
Raw Materials (b)	—		2.8
Work in Progress (b)	—		6.1
Finished Goods (b)	—		8.4
Reserve for Obsolescence (b)	—		(0.8		)
Total Inventories – Net		$78.2		$86.7


(a)	Fuel consists primarily of coal inventory at Minnesota Power.


(b)	On March 26, 2019, ALLETE completed the sale of U.S. Water Services which resulted in the removal of the related inventory items from the Consolidated Balance Sheet.

NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued)



Other Non-Current Assets	June 30, 2019		December 31, 2018
Millions
Contract Assets (a)		$29.2		$30.7
Finance Receivable (b)	—		10.4
Operating Lease Right-of-use Assets (c)	31.2		—
ALLETE Properties	22.6		24.4
Other	80.8		86.9
Total Other Non-Current Assets		$163.8		$152.4


(a)	Contract Assets consist of payments made to customers as an incentive to execute or extend service agreements. The contract payments are being amortized over the term of the respective agreements as a reduction to revenue.


(b)	Finance Receivable related to the 2016 sale of Ormond Crossings and Lake Swamp, which was collected in the second quarter of 2019.


(c)	See Leases.



Other Current Liabilities	June 30, 2019		December 31, 2018
Millions
Provision for Interim Rate Refund (a)	—			$40.0
PSAs		$12.4	12.6
Contract Liabilities (b)	—		7.6
Provision for Tax Reform Refund (c)	0.4		10.7
Contingent Consideration (d)	—		3.8
Operating Lease Liabilities (e)	7.2		—
Other	39.5		53.8
Total Other Current Liabilities		$59.5		$128.5


(a)	Provision for Interim Rate Refund was refunded to Minnesota Power’s retail customers in the second quarter of 2019.


(b)	Contract Liabilities consist of deposits received as a result of entering into contracts with our customers prior to completing our performance obligations.


(c)	Provision for Tax Reform Refund related to the income tax benefits of the TCJA in 2018 was refunded to Minnesota Power customers in the first quarter of 2019 and will be refunded to SWL&P customers in 2019 and 2020.


(d)	Contingent Consideration related to the earnings-based payment resulting from the U.S. Water Services acquisition was paid in the first quarter of 2019.


(e)	See Leases.



Other Non-Current Liabilities	June 30, 2019		December 31, 2018
Millions
Asset Retirement Obligation		$142.7		$138.6
PSAs	70.7		76.9
Operating Lease Liabilities (a)	24.0		—
Other	45.4		47.1
Total Other Non-Current Liabilities		$282.8		$262.6


(a)	See Leases.

NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued)

Supplemental Statement of Cash Flows Information.



Six Months Ended June 30,	2019		2018
Millions
Cash Paid for Interest – Net of Amounts Capitalized		$33.8		$33.0
Noncash Investing and Financing Activities
Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment	$21.1		$(39.4)
Reclassification of Property, Plant and Equipment to Inventory (a)	—			$46.3
Recognition of Right-of-use Assets and Lease Liabilities (b)	$31.2		—
Capitalized Asset Retirement Costs		$1.4		$20.8
AFUDC–Equity		$1.3		$0.5


(a)	In February 2018, Montana-Dakota Utilities exercised its option to purchase the Thunder Spirit II wind energy facility upon completion, resulting in a reclassification from Property, Plant and Equipment – Net to Inventories – Net for project costs incurred in the prior year.


(b)	See Leases.

New Accounting Pronouncements.

Recently Adopted Pronouncements

Disclosure Update and Simplification. In November 2018, the SEC adopted amendments to certain disclosure requirements. The amendments adopted include requirements that interim financial statements should include comparative statements for the same period in the prior financial year, except that the requirement for comparative balance sheet information may be satisfied by presenting the year-end balance sheet. It further includes a requirement analyzing the changes in each caption of shareholders’ equity either separately in a note or on the face of the financial statement. These amendments were effective for ALLETE in the first quarter of 2019. We have included the presentation of our Statement of Shareholders’ Equity to meet these requirements.

Leases. In 2016, the FASB issued an accounting standard update which revised the existing guidance for leases. Under the revised guidance, lessees are required to recognize right-of-use assets and lease liabilities on the Consolidated Balance Sheet for leases with terms greater than 12 months. The new standard also requires additional qualitative and quantitative disclosures by lessees and lessors to enable users of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The accounting for leases by lessors and the recognition, measurement and presentation of expenses and cash flows from leases is not expected to significantly change as a result of the new guidance. The Company adopted this guidance in the first quarter of 2019 using the optional transition method and the package of practical expedients, which allowed for the adoption of the standard as of January 1, 2019, without restating previously disclosed information. Management elected the optional transition method of adoption due to the overall immateriality of the balance sheet gross up in the period of adoption. The package of practical expedients allowed management to not reassess the lease classification for leases, including those that had expired during the periods presented or that still existed at the time of adoption. We have included additional disclosures in the notes to the consolidated financial statements. (See Leases.)

Leases. We determine if a contract is, or contains, a lease at inception and recognize a right-of-use asset and lease liability for all leases with a term greater than 12 months. Our right-of-use assets and lease liabilities for operating leases are included in Other Non-Current Assets, Other Current Liabilities and Other Non-Current Liabilities, respectively, in our Consolidated Balance Sheet. We currently do not have any finance leases.

Right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. Operating lease right-of-use assets and lease liabilities are recognized at the commencement date based on the estimated present value of lease payments over the lease term. As our leases do not provide an explicit rate, we determine the present value of future lease payments based on our estimated incremental borrowing rate using information available at the lease commencement date. The operating lease right-of-use asset includes lease payments to be made during the lease term and any lease incentives, as applicable.

NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued)

Leases (Continued)

Our leases may include options to extend or buy out the lease at certain points throughout the term, and if it is reasonably certain that we will exercise that option at lease commencement, we include those rental payments in our calculation of the right-of-use asset and lease liability. Lease and rent expense is recognized on a straight-line basis over the lease term. Leases with a term of 12 months or less are not recognized on the Consolidated Balance Sheet.

The majority of our operating leases are for heavy equipment, vehicles and land with fixed monthly payments which we group into two categories: Vehicles and Equipment; and Land and Other. Our largest operating lease is for the dragline at BNI Energy which includes a termination payment at the end of the lease term if we do not exercise our purchase option. The amount of this payment is $3 million and is included in our calculation of the right-of-use asset and lease liability recorded. None of our other leases contain residual value guarantees.

Additional information on the components of lease cost and presentation of cash flows were as follows:



	Quarter Ended		Six Months Ended
	June 30,		June 30,
	2019		2019
Millions
Operating Lease Cost		$2.8		$5.7

Other Information:
Operating Cash Flows From Operating Leases		$2.8		$5.7

Additional information related to leases was as follows:



	June 30,
	2019
Millions
Balance Sheet Information Related to Leases:
Other Non-Current Assets		$31.2
Total Operating Lease Right-of-use Assets		$31.2

Other Current Liabilities		$7.2
Other Non-Current Liabilities	24.0
Total Operating Lease Liabilities		$31.2

Weighted Average Remaining Lease Term (Years):
Operating Leases - Vehicles and Equipment	4
Operating Leases - Land and Other	29

Weighted Average Discount Rate:
Operating Leases - Vehicles and Equipment	3.2		%
Operating Leases - Land and Other	4.5		%

NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued)

Leases (Continued)

Maturities of lease liabilities were as follows:



	June 30, 2019
Millions
2019		$4.2
2020	7.9
2021	6.1
2022	4.9
2023	3.1
Thereafter	9.4
Total Lease Payments Due	35.6
Less: Imputed Interest	4.4
Total Lease Obligations	31.2
Less: Current Lease Obligations	7.2
Long-term Lease Obligations		$24.0

Sale of U.S. Water Services. On February 8, 2019, the Company entered into a stock purchase agreement providing for the sale of U.S. Water Services to a subsidiary of Kurita Water Industries Ltd. for a cash purchase price of $270 million. On March 26, 2019, ALLETE completed the sale and received approximately $265 million in cash at closing, net of transaction costs and cash retained. The Company recognized a gain on the sale of U.S. Water Services of $11.1 million after-tax in 2019.

ALLETE Clean Energy Asset Acquisition. On May 3, 2019, ALLETE Clean Energy acquired the Diamond Spring wind project in Oklahoma from Apex Clean Energy. ALLETE Clean Energy will build, own and operate the approximately 300 MW wind energy facility. The Diamond Spring wind project is fully contracted to sell wind power to Walmart Inc., Smithfield Foods, Inc. and Starbucks Corporation under long-term power sales agreements. Construction is expected to begin in late 2019 and be completed in the second half of 2020.

Subsequent Events. The Company performed an evaluation of subsequent events for potential recognition and disclosure through the date of the financial statements issuance.

Regulatory Matters

6 Months Ended

Jun. 30, 2019

Regulated Operations [Abstract]

Regulatory Matters [Text Block]

REGULATORY MATTERS

Regulatory matters are summarized in Note 4. Regulatory Matters to the Consolidated Financial Statements in our 2018 Form 10‑K, with additional disclosure provided in the following paragraphs.

Electric Rates. Entities within our Regulated Operations segment file for periodic rate revisions with the MPUC, PSCW or FERC. As authorized by the MPUC, Minnesota Power also recognizes revenue under cost recovery riders for transmission, renewable, and environmental investments and expenditures. Revenue from cost recovery riders was $17.4 million for the six months ended June 30, 2019 ($52.1 million for six months ended June 30, 2018). With the implementation of final rates in Minnesota Power’s general rate case, certain revenue previously recognized under cost recovery riders was incorporated into base rates. (See 2016 Minnesota General Rate Case.)

2016 Minnesota General Rate Case. The MPUC issued an order dated March 12, 2018, in Minnesota Power’s general rate case approving a return on common equity of 9.25 percent and a 53.81 percent equity ratio. Final rates went into effect on December 1, 2018, which is expected to result in additional revenue of approximately $13 million on an annualized basis. Interim rates were collected from January 1, 2017, through November 30, 2018, which were fully offset by the recognition of a corresponding reserve. Minnesota Power recorded a reserve for an interim rate refund, net of discounts provided to EITE customers, of $40.0 million as of December 31, 2018, which was refunded in the second quarter of 2019.

NOTE 2. REGULATORY MATTERS (Continued)

Electric Rates (Continued)

2018 Wisconsin General Rate Case. In an order dated December 20, 2018, the PSCW approved a rate increase for SWL&P including a return on equity of 10.4 percent and a 55.0 percent equity ratio. Final rates went into effect January 1, 2019, which is expected to result in additional revenue of approximately $1.3 million on an annualized basis.

Transmission Cost Recovery Rider. Minnesota Power has an approved cost recovery rider in place for certain transmission investments and expenditures. In a 2016 order, the MPUC approved Minnesota Power’s updated customer billing rates allowing Minnesota Power to charge retail customers on a current basis for the costs of constructing certain transmission facilities plus a return on the capital invested. On July 9, 2019, Minnesota Power filed a petition seeking MPUC approval to update the customer billing factor to include investments made for the GNTL.

Fuel Adjustment Clause Reform. In a December 2017 order, the MPUC adopted a program to implement certain procedural reforms to Minnesota utilities’ automatic fuel adjustment clause (FAC) for fuel and purchased power. With this order, the method of accounting for all Minnesota electric utilities changed to a monthly budgeted, forward-looking FAC with annual prudence review and true-up to actual allowed costs. On May 1, 2019, Minnesota Power filed its fuel adjustment forecast for 2020 with the MPUC.

Integrated Resource Plan. In a 2016 order, the MPUC approved Minnesota Power’s 2015 IRP with modifications. The order accepted Minnesota Power’s plans for the economic idling of Taconite Harbor Units 1 and 2 and the ceasing of coal-fired operations at Taconite Harbor in 2020, directed Minnesota Power to retire Boswell Units 1 and 2 no later than 2022, required an analysis of generation and demand response alternatives to be filed with a natural gas resource proposal, and required Minnesota Power to conduct requests for proposal for additional wind, solar and demand response resource additions. Minnesota Power retired Boswell Units 1 and 2 in the fourth quarter of 2018. Minnesota Power’s next IRP filing is due October 1, 2020.

In 2017, Minnesota Power submitted a resource package to the MPUC requesting approval of PPAs for the output of a 250 MW wind energy facility and a 10 MW solar energy facility as well as approval of a 250 MW natural gas capacity dedication agreement. The natural gas capacity dedication agreement was subject to MPUC approval of the construction of NTEC, a 525 MW to 550 MW combined-cycle natural gas-fired generating facility which will be jointly owned by Dairyland Power Cooperative and a subsidiary of ALLETE. Minnesota Power would purchase approximately 50 percent of the facility's output starting in 2025. In an order dated January 24, 2019, the MPUC approved Minnesota Power’s request for approval of the NTEC natural gas capacity dedication agreement. Separately, the MPUC required a baseload retirement evaluation in Minnesota Power’s next IRP filing analyzing its existing fleet, including potential early retirement scenarios of Boswell Units 3 and 4, as well as a securitization plan. On January 8, 2019, an application for a certificate of public convenience and necessity for NTEC was submitted to the PSCW. A decision on the application is expected in 2020.

Conservation Improvement Program. On April 1, 2019, Minnesota Power submitted its 2018 consolidated filing, which detailed Minnesota Power’s CIP program results and requested a CIP financial incentive of $2.8 million based upon MPUC procedures, which was approved by the MPUC in an order dated July 19, 2019. In 2018, the CIP financial incentive of $3.0 million was recognized in the third quarter upon approval by the MPUC of Minnesota Power’s 2017 CIP consolidated filing. CIP financial incentives are recognized in the period in which the MPUC approves the filing.

Regulatory Assets and Liabilities. Our regulated utility operations are subject to accounting guidance for the effect of certain types of regulation. Regulatory assets represent incurred costs that have been deferred as they are probable for recovery in customer rates. Regulatory liabilities represent obligations to make refunds to customers and amounts collected in rates for which the related costs have not yet been incurred. The Company assesses quarterly whether regulatory assets and liabilities meet the criteria for probability of future recovery or deferral. With the exception of the regulatory asset for Boswell Units 1 and 2 net plant and equipment, no other regulatory assets are currently earning a return. The recovery, refund or credit to rates for these regulatory assets and liabilities will occur over the periods either specified by the applicable regulatory authority or over the corresponding period related to the asset or liability.

NOTE 2. REGULATORY MATTERS (Continued)



Regulatory Assets and Liabilities	June 30, 2019		December 31, 2018
Millions
Non-Current Regulatory Assets
Defined Benefit Pension and Other Postretirement Benefit Plans		$216.5		$218.5
Income Taxes	102.2		105.5
Asset Retirement Obligations	32.3		32.6
Boswell 1 and 2 Net Plant and Equipment	13.5		16.3
Cost Recovery Riders	10.0		—
Manufactured Gas Plant	8.1		8.0
PPACA Income Tax Deferral	4.9		5.0
Other	3.7		3.6
Total Non-Current Regulatory Assets		$391.2		$389.5

Current Regulatory Liabilities (a)
Provision for Interim Rate Refund (b)	—			$40.0
Transmission Formula Rates Refund		$3.1	4.4
Provision for Tax Reform Refund (c)	0.4		10.7
Total Current Regulatory Liabilities	3.5		55.1
Non-Current Regulatory Liabilities
Income Taxes	386.2		396.4
Wholesale and Retail Contra AFUDC	70.6		64.4
Plant Removal Obligations	29.3		25.1
North Dakota Investment Tax Credits	12.3		14.7
Conservation Improvement Program	7.0		1.5
Transmission Formula Rates Refund	0.8		1.6
Cost Recovery Riders	—		6.9
Other	2.6		1.5
Total Non-Current Regulatory Liabilities	508.8		512.1
Total Regulatory Liabilities		$512.3		$567.2


(a)	Current regulatory liabilities are presented within Other Current Liabilities on the Consolidated Balance Sheet.


(b)	This amount was refunded to Minnesota Power’s regulated retail customers in the second quarter of 2019.

(c)

Provision for Tax Reform Refund related to the income tax benefits of the TCJA in 2018 was refunded to Minnesota Power customers in the first quarter of 2019 and will be refunded to SWL&P customers in 2019 and 2020.

Equity Investments

6 Months Ended

Jun. 30, 2019

Equity Method Investments and Joint Ventures [Abstract]

Investment in ATC [Text Block]

EQUITY INVESTMENTS

Investment in ATC. Our wholly-owned subsidiary, ALLETE Transmission Holdings, owns approximately 8 percent of ATC, a Wisconsin-based utility that owns and maintains electric transmission assets in portions of Wisconsin, Michigan, Minnesota and Illinois. We account for our investment in ATC under the equity method of accounting. In the six months ended June 30, 2019, we invested $2.7 million in ATC, and on July 31, 2019, we invested an additional $1.9 million. We expect to make approximately $4 million in additional investments in 2019.



ALLETE’s Investment in ATC
Millions
Equity Investment Balance as of December 31, 2018		$128.1
Cash Investments	2.7
Equity in ATC Earnings	10.4
Distributed ATC Earnings	(8.2		)
Amortization of the Remeasurement of Deferred Income Taxes	0.6
Equity Investment Balance as of June 30, 2019		$133.6

ATC’s authorized return on equity is 10.32 percent, or 10.82 percent including an incentive adder for participation in a regional transmission organization.

NOTE 3. EQUITY INVESTMENTS (Continued)

Investment in ATC (Continued)

In 2016, a federal administrative law judge ruled on a complaint proposing a reduction in the base return on equity to 9.70 percent, or 10.20 percent including an incentive adder for participation in a regional transmission organization, subject to approval or adjustment by the FERC. A final decision from the FERC on the administrative law judge’s recommendation is pending.

Investment in Nobles 2. Our wholly-owned subsidiary, ALLETE South Wind, owns 49 percent of Nobles 2, the entity that will own and operate a 250 MW wind energy facility in southwestern Minnesota pursuant to a 20-year PPA with Minnesota Power. We account for our investment in Nobles 2 under the equity method of accounting. As of June 30, 2019, our equity investment in Nobles 2 was $26.6 million ($33.0 million at December 31, 2018). In the first quarter of 2019, Nobles 2 returned capital of $8.3 million based on its cash needs. We expect to make approximately $33 million in additional investments in 2019.

Fair Value

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value [Text Block]

FAIR VALUE

Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). We utilize market data or assumptions that market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs can be readily observable, market corroborated or generally unobservable. We primarily apply the market approach for recurring fair value measurements and endeavor to utilize the best available information. Accordingly, we utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. These inputs, which are used to measure fair value, are prioritized through the fair value hierarchy. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). Descriptions of the three levels of the fair value hierarchy are discussed in Note 9. Fair Value to the Consolidated Financial Statements in our 2018 Form 10-K.

NOTE 5. FAIR VALUE (Continued)

The following tables set forth, by level within the fair value hierarchy, our assets and liabilities that were accounted for at fair value on a recurring basis as of June 30, 2019, and December 31, 2018. Each asset and liability is classified based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment, which may affect the valuation of these assets and liabilities and their placement within the fair value hierarchy levels. The estimated fair value of Cash and Cash Equivalents listed on the Consolidated Balance Sheet approximates the carrying amount and therefore is excluded from the recurring fair value measures in the following tables.



	Fair Value as of June 30, 2019
Recurring Fair Value Measures	Level 1		Level 2		Level 3		Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities		$10.9	—		—			$10.9
Available-for-sale – Corporate and Governmental Debt Securities (b)	—			$9.5	—		9.5
Cash Equivalents	1.1		—		—		1.1
Total Fair Value of Assets		$12.0		$9.5	—			$21.5

Liabilities
Deferred Compensation (c)	—			$21.7	—			$21.7
Total Fair Value of Liabilities	—			$21.7	—			$21.7
Total Net Fair Value of Assets (Liabilities)		$12.0	$(12.2)		—		$(0.2)


	Fair Value as of December 31, 2018
Recurring Fair Value Measures	Level 1		Level 2		Level 3		Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities		$12.2	—		—			$12.2
Available-for-sale – Corporate and Governmental Debt Securities	—			$8.0	—		8.0
Cash Equivalents	1.0		—		—		1.0
Total Fair Value of Assets		$13.2		$8.0	—			$21.2

Liabilities
Deferred Compensation (c)	—			$19.8	—			$19.8
U.S. Water Services Contingent Consideration (d)	—		—			$3.8	3.8
Total Fair Value of Liabilities	—			$19.8		$3.8		$23.6
Total Net Fair Value of Assets (Liabilities)		$13.2	$(11.8)		$(3.8)		$(2.4)


(a)	Included in Other Non-Current Assets on the Consolidated Balance Sheet.


(b)	As of June 30, 2019, the aggregate amount of available-for-sale corporate and governmental debt securities maturing in one year or less was $3.1 million, in one year to less than three years was $3.9 million, in three years to less than five years was $1.6 million and in five or more years was $0.9 million.


(c)	Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.


(d)	Included in Other Current Liabilities on the Consolidated Balance Sheet.

The Level 3 liability in the preceding table is related to the contingent consideration liability that resulted from the 2015 acquisition of U.S. Water Services. Based on the terms and conditions of the acquisition agreement, a final payout of $3.8 million was made in the first quarter of 2019 for the remaining outstanding shares.

Fair Value of Financial Instruments. With the exception of the item listed in the following table, the estimated fair value of all financial instruments approximates the carrying amount. The fair value for the item listed in the following table was based on quoted market prices for the same or similar instruments (Level 2).

NOTE 5. FAIR VALUE (Continued)



Financial Instruments	Carrying Amount	Fair Value
Millions
Long-Term Debt, Including Long-Term Debt Due Within One Year
June 30, 2019	$1,543.0	$1,684.3
December 31, 2018	$1,495.2	$1,534.6

Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis. Non-financial assets such as equity method investments, land inventory, and property, plant and equipment are measured at fair value when there is an indicator of impairment and recorded at fair value only when an impairment is recognized. For the quarter and six months ended June 30, 2019, and the year ended December 31, 2018, there were no triggering events or indicators of impairment for these non-financial assets.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Short-Term and Long-Term Debt

6 Months Ended

Jun. 30, 2019

Debt Disclosure [Abstract]

Short-Term and Long-Term Debt [Text Block]

SHORT-TERM AND LONG-TERM DEBT

The following tables present the Company’s short-term and long-term debt as of June 30, 2019, and December 31, 2018:



June 30, 2019	Principal		Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt		$28.1	$(0.4)		$27.7
Long-Term Debt	1,514.9		(9.0)	1,505.9
Total Debt		$1,543.0	$(9.4)		$1,533.6



December 31, 2018	Principal		Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt		$57.9	$(0.4)		$57.5
Long-Term Debt	1,437.3		(8.8)	1,428.5
Total Debt		$1,495.2	$(9.2)		$1,486.0

On January 10, 2019, ALLETE entered into an amended and restated $400 million credit agreement, as amended (Credit Agreement). The Credit Agreement is unsecured, has a variable interest rate and will expire in January 2024. At ALLETE’s request and subject to certain conditions, the Credit Agreement may be increased by up to $150 million and ALLETE may make two requests to extend the maturity date, each for a one-year extension. Advances may be used by ALLETE for general corporate purposes, to provide liquidity in support of ALLETE’s commercial paper program and to issue up to $100 million in letters of credit.

We had $56.3 million outstanding in standby letters of credit and no outstanding draws under our lines of credit as of June 30, 2019 ($18.4 million in standby letters of credit and no outstanding draws as of December 31, 2018).

On March 1, 2019, ALLETE issued and sold the following First Mortgage Bonds (the Bonds):



Maturity Date	Principal Amount	Interest Rate
March 1, 2029	$70 Million	4.08%
March 1, 2049	$30 Million	4.47%

ALLETE has the option to prepay all or a portion of the Bonds at its discretion, subject to a make-whole provision. The Bonds are subject to additional terms and conditions which are customary for these types of transactions. ALLETE intends to use the proceeds from the sale of the Bonds to fund utility capital investment and for general corporate purposes. The Bonds were sold in reliance on an exemption from registration under Section 4(a)(2) of the Securities Act of 1933, as amended, to institutional accredited investors.

NOTE 6. SHORT-TERM AND LONG-TERM DEBT (Continued)

Financial Covenants. Our long-term debt arrangements contain customary covenants. In addition, our lines of credit and letters of credit supporting certain long-term debt arrangements contain financial covenants. Our compliance with financial covenants is not dependent on debt ratings. The most restrictive financial covenant requires ALLETE to maintain a ratio of indebtedness to total capitalization (as the amounts are calculated in accordance with the respective long-term debt arrangements) of less than or equal to 0.65 to 1.00, measured quarterly. As of June 30, 2019, our ratio was approximately 0.42 to 1.00. Failure to meet this covenant would give rise to an event of default if not cured after notice from the lender, in which event ALLETE may need to pursue alternative sources of funding. Some of ALLETE’s debt arrangements contain “cross-default” provisions that would result in an event of default if there is a failure under other financing arrangements to meet payment terms or to observe other covenants that would result in an acceleration of payments due. ALLETE has no significant restrictions on its ability to pay dividends from retained earnings or net income. As of June 30, 2019, ALLETE was in compliance with its financial covenants.

Commitments, Guarantees and Contingencies

6 Months Ended

Jun. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments, Guarantees and Contingencies [Text Block]

COMMITMENTS, GUARANTEES AND CONTINGENCIES

Power Purchase Agreements. Our long-term PPAs have been evaluated under the accounting guidance for variable interest entities. We have determined that either we have no variable interest in the PPAs or, where we do have variable interests, we are not the primary beneficiary; therefore, consolidation is not required. These conclusions are based on the fact that we do not have both control over activities that are most significant to the entity and an obligation to absorb losses or receive benefits from the entity’s performance. Our financial exposure relating to these PPAs is limited to our capacity and energy payments.

Our PPAs are summarized in Note 11. Commitments, Guarantees and Contingencies to the Consolidated Financial Statements in our 2018 Form 10-K, with additional disclosure provided in the following paragraphs.

Square Butte PPA. As of June 30, 2019, Square Butte had total debt outstanding of $301.9 million. Fuel expenses are recoverable through Minnesota Power’s fuel adjustment clause and include the cost of coal purchased from BNI Energy under a long-term contract. Minnesota Power’s cost of power purchased from Square Butte during the six months ended June 30, 2019, was $41.1 million ($37.7 million for the six months ended June 30, 2018). This reflects Minnesota Power’s pro rata share of total Square Butte costs based on the 50 percent output entitlement. Included in this amount was Minnesota Power’s pro rata share of interest expense of $4.2 million ($4.6 million for the same period in 2018). Minnesota Power’s payments to Square Butte are approved as a purchased power expense for ratemaking purposes by both the MPUC and the FERC.

Minnkota Power PSA. Minnesota Power has a PSA with Minnkota Power, which commenced in 2014. Under the PSA, Minnesota Power is selling a portion of its entitlement from Square Butte to Minnkota Power, resulting in Minnkota Power’s net entitlement increasing and Minnesota Power’s net entitlement decreasing until Minnesota Power’s share is eliminated at the end of 2025. Of Minnesota Power’s 50 percent output entitlement, it sold to Minnkota Power approximately 28 percent in 2019 and in 2018.

Coal, Rail and Shipping Contracts. Minnesota Power has coal supply agreements providing for the purchase of a significant portion of its coal requirements through December 2019 and a portion of its coal requirements through December 2021. Minnesota Power also has coal transportation agreements in place for the delivery of a significant portion of its coal requirements through December 2021. The costs of fuel and related transportation costs for Minnesota Power’s generation are recoverable from Minnesota Power’s utility customers through the fuel adjustment clause.

Transmission. We continue to make investments in transmission opportunities that strengthen or enhance the transmission grid or take advantage of our geographical location between sources of renewable energy and end users. These include the GNTL, investments to enhance our own transmission facilities, investments in other transmission assets (individually or in combination with others) and our investment in ATC.

Great Northern Transmission Line. As a condition of the 250-MW long-term PPA entered into with Manitoba Hydro, construction of additional transmission capacity is required. As a result, Minnesota Power is constructing the GNTL, an approximately 220‑mile 500-kV transmission line between Manitoba and Minnesota’s Iron Range that was proposed by Minnesota Power and Manitoba Hydro in order to strengthen the electric grid, enhance regional reliability and promote a greater exchange of sustainable energy.

NOTE 7. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued)

Transmission (Continued)

In a 2016 order, the MPUC approved the route permit for the GNTL, and in 2016, the U.S. Department of Energy issued a presidential permit to cross the U.S.‑Canadian border, which was the final major regulatory approval needed before construction in the U.S. could begin. Construction activities commenced in the first quarter of 2017, and with construction on schedule, Minnesota Power expects the GNTL to be complete and in-service by mid-2020. The total project cost in the U.S., including substation work, is estimated to be approximately $750 million, of which Minnesota Power’s portion is expected to be approximately $345 million; the difference will be recovered from a subsidiary of Manitoba Hydro as non-shareholder contributions to capital. Total project costs of $510.8 million have been incurred through June 30, 2019, of which $272.7 million has been recovered from a subsidiary of Manitoba Hydro.

In 2015, Manitoba Hydro submitted the final preferred route and EIS for the MMTP to the Manitoba Conservation and Water Stewardship for siting and environmental approval, which was received on April 4, 2019. In 2016, Manitoba Hydro filed an application with the Canadian National Energy Board (NEB) requesting authorization to construct and operate the MMTP, which was recommended for approval on November 15, 2018. On June 14, 2019, Manitoba Hydro announced Canada’s federal government approved the MMTP project, subject to certain compliance conditions.

The MMTP is subject to legal and regulatory challenges which Minnesota Power is actively monitoring. Manitoba Hydro has informed Minnesota Power that it continues to work towards completing the MMTP on schedule. In order to meet the transmission in‑service requirements in PPAs with Minnesota Power, Manitoba Hydro has indicated that it would need to start construction of the MMTP by September 2019. We are unable to predict the outcome of the Canadian regulatory review process, including the timing thereof or whether any onerous conditions may be imposed, or the timing of the completion of the MMTP, including the impact of any delays that may result in construction schedule adjustments. In the event the MMTP is delayed and not in-service by June 1, 2020, Minnesota Power has construction and related agreements in place with Manitoba Hydro and a Manitoba Hydro subsidiary that will protect Minnesota Power and its customers.

Construction of Manitoba Hydro’s Keeyask hydroelectric generation facility, which will provide the power to be sold under PPAs with Minnesota Power and transmitted on the MMTP and the GNTL, commenced in 2014 and is anticipated to be in service by early 2021.

Environmental Matters.

Our businesses are subject to regulation of environmental matters by various federal, state and local authorities. A number of regulatory changes to the Clean Air Act, the Clean Water Act and various waste management requirements have been promulgated by both the EPA and state authorities over the past several years. Minnesota Power’s facilities are subject to additional requirements under many of these regulations. Minnesota Power is reshaping its generation portfolio, over time, to reduce its reliance on coal, has installed cost-effective emission control technology, and advocates for sound science and policy during rulemaking implementation.

We consider our businesses to be in substantial compliance with currently applicable environmental regulations and believe all necessary permits have been obtained. We anticipate that with many state and federal environmental regulations and requirements finalized, or to be finalized in the near future, potential expenditures for future environmental matters may be material and require significant capital investments. Minnesota Power has evaluated various environmental compliance scenarios using possible outcomes of environmental regulations to project power supply trends and impacts on customers.

We review environmental matters on a quarterly basis. Accruals for environmental matters are recorded when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated based on current law and existing technologies. Accruals are adjusted as assessment and remediation efforts progress, or as additional technical or legal information becomes available. Accruals for environmental liabilities are included in the Consolidated Balance Sheet at undiscounted amounts and exclude claims for recoveries from insurance or other third parties. Costs related to environmental contamination treatment and cleanup are expensed unless recoverable in rates from customers.

Air. The electric utility industry is regulated both at the federal and state level to address air emissions. Minnesota Power’s generating facilities mainly burn low-sulfur western sub-bituminous coal. All of Minnesota Power’s coal-fired generating facilities are equipped with pollution control equipment such as scrubbers, baghouses and low NO_X technologies. Under currently applicable environmental regulations, these facilities are substantially compliant with emission requirements.

NOTE 7. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued)

Environmental Matters (Continued)

Cross-State Air Pollution Rule (CSAPR). The CSAPR requires certain states in the eastern half of the U.S., including Minnesota, to reduce power plant emissions that contribute to ozone or fine particulate pollution in other states. The CSAPR does not require installation of controls but does require facilities have sufficient allowances to cover their emissions on an annual basis. These allowances are allocated to facilities from each state’s annual budget, and can be bought and sold. Based on our review of the NO_x and SO₂ allowances issued and pending issuance, we currently expect generation levels and emission rates will result in continued compliance with the CSAPR.

National Ambient Air Quality Standards (NAAQS). The EPA is required to review the NAAQS every five years. If the EPA determines that a state’s air quality is not in compliance with the NAAQS, the state is required to adopt plans describing how it will reduce emissions to attain the NAAQS. None of the compliance costs for proposed or current NAAQS revisions are expected to be material.

Climate Change. The scientific community generally accepts that emissions of GHG are linked to global climate change which creates physical and financial risks. Physical risks could include, but are not limited to: increased or decreased precipitation and water levels in lakes and rivers; increased temperatures; and changes in the intensity and frequency of extreme weather events. These all have the potential to affect the Company’s business and operations. We are addressing climate change by taking the following steps that also ensure reliable and environmentally compliant generation resources to meet our customers’ requirements:


•	Expanding renewable power supply for both our operations and the operations of others;


•	Providing energy conservation initiatives for our customers and engaging in other demand side management efforts;


•	Improving efficiency of our generating facilities;


•	Supporting research of technologies to reduce carbon emissions from generating facilities and carbon sequestration efforts;


•	Evaluating and developing less carbon intensive future generating assets such as efficient and flexible natural gas-fired generating facilities;


•	Managing vegetation on right-of-way corridors to reduce potential wildfire or storm damage risks; and


•	Practicing sound forestry management in our service territories to create landscapes more resilient to disruption from climate-related changes, including planting and managing long-lived conifer species.

EPA Regulation of GHG Emissions. On June 19, 2019, the EPA finalized several separate rulemakings regarding regulating carbon emissions from electric utility generating units.

The EPA repealed the Clean Power Plan (CPP), following a determination by the EPA that the CPP exceeded the EPA’s statutory authority under the Clean Air Act (CAA). The primary reason for this was that the CPP attempted to regulate electric generating unit’s carbon emissions through measures outside of the affected unit’s direct control. The CPP was first announced as a proposed rule under Section 111(d) of the Clean Air Act for existing power plants entitled “Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Generating Units”.

With the repeal of the CPP, the Affordable Clean Energy Rule was finalized. The rule establishes emissions guidelines for states to use when developing plans to limit carbon dioxide at coal-fired power plants. The rule identifies heat rate improvements made at individual units as the best system of emission reduction. Affected facilities for Minnesota Power include Boswell Units 3 and 4. Based on our initial review of the rule, many of the candidate heat rate improvements are already installed on Boswell Units 3 and 4.

Additionally, the EPA finalized new regulations for the state implementation of the Affordable Clean Energy Rule and any future emission guidelines issued under CAA Section 111(d). States will have three years to submit State Implementation Plans (SIP), and the EPA has 12 months to review and approve those plans. Since the Affordable Clean Energy Rule allows states considerable flexibility in how to best implement its requirements, Minnesota Power plans to work closely with the MPCA and the Minnesota Department of Commerce, who are currently co-reviewing the rule as the state develops its SIP. If a state does not submit a SIP or submits a SIP that is unacceptable to the EPA, the EPA will develop a Federal Implementation Plan.

Minnesota had already initiated several measures consistent with those called for under the now repealed CPP and finalized Affordable Clean Energy Rule. Minnesota Power continues implementing its EnergyForward strategic plan that provides for significant emission reductions and diversifying its electricity generation mix to include more renewable and natural gas energy. (See Note 2. Regulatory Matters.) We are unable to predict the GHG emission compliance costs we might incur as a result of the Affordable Clean Energy Rule and the resulting SIP; however, the costs could be material. Minnesota Power would seek recovery of additional costs through a rate proceeding.

NOTE 7. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued)

Environmental Matters (Continued)

Water. The Clean Water Act requires NPDES permits be obtained from the EPA (or, when delegated, from individual state pollution control agencies) for any wastewater discharged into navigable waters. We have obtained all necessary NPDES permits, including NPDES storm water permits for applicable facilities, to conduct our operations.

Steam Electric Power Generating Effluent Limitations Guidelines. In 2015, the EPA issued revised federal effluent limitation guidelines (ELG) for steam electric power generating stations under the Clean Water Act. It set effluent limits and prescribed BACT for several wastewater streams, including flue gas desulphurization (FGD) water, bottom ash transport water and coal combustion landfill leachate. In 2017, the EPA announced a two-year postponement of the ELG compliance date of November 1, 2018, to November 1, 2020, while the agency reconsiders the bottom ash transport water and FGD wastewater provisions. On April 12, 2019, the U.S. Court of Appeals for the Fifth Circuit vacated and remanded back to the EPA portions of the ELG that allowed for continued discharge of legacy wastewater and leachate.

The final ELG's potential impact on Minnesota Power operations is primarily at Boswell. Boswell currently discharges bottom ash contact water through its NPDES permit, and also has a closed-loop FGD system that does not discharge to surface waters, but may do so in the future. Under the existing ELG rule, bottom ash transport water discharge to surface waters must cease no later than December 31, 2023. Bottom ash contact water will either need to be re-used in a closed-loop process, routed to a FGD scrubber, or the bottom ash handling system will need to be converted to a dry process. If FGD wastewater is discharged in the future, it will require additional wastewater treatment. The ELG rule provision regarding these two waste-streams are being reconsidered and may change prior to November 1, 2020. Efforts have been underway at Boswell to reduce the amount of water discharged and evaluate potential re‑use options in its plant processes. The EPA’s additional reconsideration of legacy wastewater discharge requirements have the potential to reduce time lines for dewatering Boswell’s existing bottom ash pond. The timing of a draft rule addressing legacy wastewater and leachate is currently unknown.

At this time, we cannot estimate what compliance costs we might incur related to these or other potential future water discharge regulations; however, the costs could be material, including costs associated with retrofits for bottom ash handling, pond dewatering, pond closure, and wastewater treatment and re-use. Minnesota Power would seek recovery of additional costs through a rate proceeding.

Solid and Hazardous Waste. The Resource Conservation and Recovery Act of 1976 regulates the management and disposal of solid and hazardous wastes. We are required to notify the EPA of hazardous waste activity and, consequently, routinely submit reports to the EPA.

Coal Ash Management Facilities. Minnesota Power stores or disposes coal ash at four of its electric generating facilities by the following methods: storing ash in lined onsite impoundments (ash ponds), disposing of dry ash in a lined dry ash landfill, applying ash to land as an approved beneficial use and trucking ash to state permitted landfills.

Coal Combustion Residuals from Electric Utilities (CCR). In 2015, the EPA published the final rule regulating CCR as nonhazardous waste under Subtitle D of the Resource Conservation and Recovery Act (RCRA) in the Federal Register. The rule includes additional requirements for new landfill and impoundment construction as well as closure activities related to certain existing impoundments. Costs of compliance for Boswell and Laskin are expected to occur primarily over the next 15 years and be between approximately $65 million and $120 million. The EPA has indicated to Minnesota Power that the landfill at Taconite Harbor, which has been idled and has a temporary landfill cover in place, is a CCR unit based on the EPA’s interpretation of the CCR rule language.

Minnesota Power has agreed to post the required CCR information for the Taconite Harbor landfill on Minnesota Power’s website while the CCR issue is resolved. Compliance costs for CCR at Taconite Harbor are not expected to be material. Minnesota Power would seek recovery of additional costs through a rate proceeding.

Minnesota Power continues to work on minimizing costs through evaluation of beneficial re-use and recycling of CCR and CCR‑related waters. In 2017, the EPA announced its intention to formally reconsider the CCR rule under Subtitle D of the RCRA and in March 2018, published the first phase of the proposed rule revisions in the Federal Register. In July 2018, the EPA finalized revisions to elements of the CCR rule, including extending certain deadlines by two years, the establishment of alternative groundwater protection standards for certain constituents and the potential for risk‑based management options at facilities based on site characteristics. In August 2018, a U.S. District Court for the District of Columbia decision vacated specific provisions of the CCR rule. The court decision changes the status of three existing impoundments at Boswell that must now be considered unlined. Compliance costs at Boswell due to the court decision are unknown at this time. Minnesota Power would seek recovery of additional costs through a rate proceeding.

NOTE 7. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued)

Environmental Matters (Continued)

Other Environmental Matters

Manufactured Gas Plant Site. We are reviewing and addressing environmental conditions at a former manufactured gas plant site located in Superior, Wisconsin. SWL&P has been working with the Wisconsin Department of Natural Resources (WDNR) in determining the extent of contamination at the site and surrounding properties. In December 2017, the WDNR authorized SWL&P to transition from site investigation into the remedial design process. As of June 30, 2019, we have recorded a liability of approximately $7 million for remediation costs at this site (approximately $7 million as of December 31, 2018), and an associated regulatory asset as we expect recovery of these remediation costs to be allowed by the PSCW. Remediation costs are expected to be incurred through 2023.

Other Matters.

ALLETE Clean Energy. ALLETE Clean Energy’s wind energy facilities have PSAs in place for their entire output and expire in various years between 2019 and 2032. As of June 30, 2019, ALLETE Clean Energy has $58.4 million outstanding in standby letters of credit.

BNI Energy. As of June 30, 2019, BNI Energy had surety bonds outstanding of $66.5 million related to the reclamation liability for closing costs associated with its mine and mine facilities. Although its coal supply agreements obligate the customers to provide for the closing costs, additional assurance is required by federal and state regulations. BNI Energy’s total reclamation liability is currently estimated at $65.8 million. BNI Energy does not believe it is likely that any of these outstanding surety bonds will be drawn upon.

ALLETE Properties. As of June 30, 2019, ALLETE Properties had surety bonds outstanding and letters of credit to governmental entities totaling $8.6 million primarily related to development and maintenance obligations for various projects. The estimated cost of the remaining development work is $6.1 million. ALLETE Properties does not believe it is likely that any of these outstanding surety bonds or letters of credit will be drawn upon.

Community Development District Obligations. As of June 30, 2019, we owned 66 percent of the assessable land in the Town Center District (68 percent as of December 31, 2018) and 12 percent of the assessable land in the Palm Coast Park District (19 percent as of December 31, 2018). As of June 30, 2019, ownership levels, our annual assessments related to capital improvement and special assessment bonds for the ALLETE Properties projects within these districts are approximately $1.4 million for Town Center at Palm Coast and $0.6 million for Palm Coast Park. As we sell property at these projects, the obligation to pay special assessments will pass to the new landowners. In accordance with accounting guidance, these bonds are not reflected as debt on our Consolidated Balance Sheet.

Legal Proceedings.

We are involved in litigation arising in the normal course of business. Also in the normal course of business, we are involved in tax, regulatory and other governmental audits, inspections, investigations and other proceedings that involve state and federal taxes, safety, and compliance with regulations, rate base and cost of service issues, among other things. We do not expect the outcome of these matters to have a material effect on our financial position, results of operations or cash flows.

Income Tax Expense

6 Months Ended

Jun. 30, 2019

Income Tax Disclosure [Abstract]

Income Tax Expense [Text Block]

INCOME TAX EXPENSE



	Quarter Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019			2018
Millions
Current Income Tax Expense (Benefit) (a)
Federal	—		—		—			—
State	$(0.1)		$(0.3)			$0.2			$0.4
Total Current Income Tax Expense (Benefit)	$(0.1)		$(0.3)			$0.2			$0.4
Deferred Income Tax Expense (Benefit)
Federal (b)	$(7.1)		$(7.4)		$(16.8)			$(14.2)
State (c)	2.5		2.4		15.0			5.0
Investment Tax Credit Amortization	(0.1	)	(0.1	)	(0.3		)	(0.3		)
Total Deferred Income Tax Benefit	$(4.7)		$(5.1)		$(2.1)			$(9.5)
Total Income Tax Benefit	$(4.8)		$(5.4)		$(1.9)			$(9.1)

(a)

For each of the six months ended June 30, 2019, and 2018, the federal and state current tax expense was minimal due to NOLs which resulted from the bonus depreciation provisions of the Protecting Americans from Tax Hikes Act of 2015, the Tax Increase Prevention Act of 2014 and the American Taxpayer Relief Act of 2012. Federal and state NOLs are being carried forward to offset current and future taxable income.


(b)	For each of the six months ended June 30, 2019, and 2018, the federal income tax benefit is primarily due to production tax credits.


(c)	For the six months ended June 30, 2019, the state income tax expense is primarily due to the sale of U.S. Water Services.

The Company's tax provision for interim periods is determined using an estimate of its annual effective tax rate, adjusted for discrete items arising in that quarter. In each quarter, the Company updates its estimate of the annual effective tax rate and if the estimated annual effective tax rate changes, the Company would make a cumulative adjustment in that quarter.

NOTE 9. INCOME TAX EXPENSE (Continued)



	Quarter Ended						Six Months Ended
Reconciliation of Taxes from Federal Statutory	June 30,						June 30,
Rate to Total Income Tax Expense	2019			2018			2019			2018
Millions
Income Before Income Taxes		$29.4			$25.9			$102.8			$73.2
Statutory Federal Income Tax Rate	21		%	21		%	21		%	21		%
Income Taxes Computed at Statutory Federal Rate		$6.2			$5.4			$21.6			$15.4
Increase (Decrease) in Income Tax Due to:
State Income Taxes – Net of Federal Income Tax Benefit	1.9			1.6			12.0			4.2
Production Tax Credits	(9.8		)	(11.2		)	(26.1		)	(25.6		)
Regulatory Differences – Excess Deferred Tax	(1.6		)	(2.2		)	(4.8		)	(4.4		)
U.S. Water Services Sale of Stock Basis Difference	(0.7		)	—			1.7			—
Share-Based Compensation	—			—			(0.9		)	(0.5		)
Other	(0.8		)	1.0			(5.4		)	1.8
Total Income Tax Benefit	$(4.8)			$(5.4)			$(1.9)			$(9.1)

For the six months ended June 30, 2019, the effective tax rate was a benefit of 1.8 percent (benefit of 12.4 percent for the six months ended June 30, 2018). The effective tax rate for 2019 was a lower benefit primarily due to a higher tax rate on the gain on the sale of U.S. Water Services and higher pre-tax income.

Uncertain Tax Positions. As of June 30, 2019, we had gross unrecognized tax benefits of $1.3 million ($1.6 million as of December 31, 2018). Of the total gross unrecognized tax benefits, $0.6 million represents the amount of unrecognized tax benefits included on the Consolidated Balance Sheet that, if recognized, would favorably impact the effective income tax rate. The unrecognized tax benefit amounts have been presented as reductions to the tax benefits associated with NOL and tax credit carryforwards on the Consolidated Balance Sheet.

ALLETE and its subsidiaries file a consolidated federal income tax return as well as combined and separate state income tax returns in various jurisdictions. ALLETE has no open federal or state audits, and is no longer subject to federal examination for years before 2015, or state examination for years before 2014.

Business Segments

6 Months Ended

Jun. 30, 2019

Segment Reporting [Abstract]

Business Segments [Text Block]

BUSINESS SEGMENTS

We present three reportable segments: Regulated Operations, ALLETE Clean Energy and U.S. Water Services. We measure performance of our operations through budgeting and monitoring of contributions to consolidated net income by each business segment.

Regulated Operations includes three operating segments which consist of our regulated utilities, Minnesota Power and SWL&P, as well as our investment in ATC. ALLETE Clean Energy is our business focused on developing, acquiring and operating clean and renewable energy projects. U.S. Water Services was our integrated water management company, which reflects operating results until the closing date of its sale on March 26, 2019. The ALLETE Clean Energy and U.S. Water Services reportable segments comprise our Energy Infrastructure and Related Services businesses. We also present Corporate and Other which includes two operating segments, BNI Energy, our coal mining operations in North Dakota, and ALLETE Properties, our legacy Florida real estate investment, along with our investment in Nobles 2, other business development and corporate expenditures, unallocated interest expense, a small amount of non-rate base generation, approximately 4,000 acres of land in Minnesota, and earnings on cash and investments.

NOTE 11. BUSINESS SEGMENTS (Continued)



	Quarter Ended					Six Months Ended
	June 30,					June 30,
	2019		2018			2019			2018
Millions
Operating Revenue
Regulated Operations
Residential		$29.2		$30.7			$74.4			$71.4
Commercial	34.9		36.2			73.8			72.8
Municipal	12.2		13.7			27.6			27.7
Industrial	120.3		115.3			241.9			230.2
Other Power Suppliers	35.2		42.7			74.6			86.4
Other	18.0		19.2			39.7			39.5
Total Regulated Operations	249.8		257.8			532.0			528.0

Energy Infrastructure and Related Services

ALLETE Clean Energy
Long-term PSA	12.5		12.4			27.1			31.0
Other	2.9		5.9			5.8			11.9
Total ALLETE Clean Energy	15.4		18.3			32.9			42.9

U.S. Water Services (a)
Point-in-Time	—		25.7			19.0			48.0
Contract	—		9.5			9.2			19.0
Capital Project	—		6.3			5.2			12.7
Total U.S. Water Services	—		41.5			33.4			79.7

Corporate and Other
Long-term Contract	21.2		22.7			41.4			42.7
Other	4.0		3.8			7.9			9.0
Total Corporate and Other	25.2		26.5			49.3			51.7
Total Operating Revenue		$290.4		$344.1			$647.6			$702.3
Net Income (Loss)
Regulated Operations		$30.3		$26.0			$81.8			$69.9

Energy Infrastructure and Related Services
ALLETE Clean Energy	1.9		6.8			7.7			14.9
U.S. Water Services (a)	—		0.2			(1.1		)	(1.2		)

Corporate and Other (a)	2.0		(1.7		)	16.3			(1.3		)
Total Net Income		$34.2		$31.3			$104.7			$82.3


(a)	On March 26, 2019, ALLETE completed the sale of U.S. Water Services. The Company recognized a gain on the sale of $11.1 million after-tax reflected in Corporate and Other in 2019. (See Note 1. Operations and Significant Accounting Policies.)



	June 30, 2019		December 31, 2018
Millions
Assets
Regulated Operations		$4,004.4		$3,952.5

Energy Infrastructure and Related Services
ALLETE Clean Energy	755.0		606.6
U.S. Water Services (a)	—		295.8

Corporate and Other	417.1		310.1
Total Assets		$5,176.5		$5,165.0

(a)

On March 26, 2019, ALLETE completed the sale of U.S. Water Services. (See Note 1. Operations and Significant Accounting Policies.)

Operations and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and Cash Equivalents, Policy [Policy Text Block]	We consider all investments purchased with original maturities of three months or less to be cash equivalents.
Inventories – Net [Policy Text Block]	Inventories are stated at the lower of cost or net realizable value. Inventories in our Regulated Operations segment are carried at an average cost or first-in, first-out basis. Inventories in our ALLETE Clean Energy segment and Corporate and Other businesses are carried at an average cost, first-in, first-out or specific identification basis.
New Accounting Standards [Policy Text Block]	New Accounting Pronouncements. Recently Adopted Pronouncements Disclosure Update and Simplification. In November 2018, the SEC adopted amendments to certain disclosure requirements. The amendments adopted include requirements that interim financial statements should include comparative statements for the same period in the prior financial year, except that the requirement for comparative balance sheet information may be satisfied by presenting the year-end balance sheet. It further includes a requirement analyzing the changes in each caption of shareholders’ equity either separately in a note or on the face of the financial statement. These amendments were effective for ALLETE in the first quarter of 2019. We have included the presentation of our Statement of Shareholders’ Equity to meet these requirements. Leases. In 2016, the FASB issued an accounting standard update which revised the existing guidance for leases. Under the revised guidance, lessees are required to recognize right-of-use assets and lease liabilities on the Consolidated Balance Sheet for leases with terms greater than 12 months. The new standard also requires additional qualitative and quantitative disclosures by lessees and lessors to enable users of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The accounting for leases by lessors and the recognition, measurement and presentation of expenses and cash flows from leases is not expected to significantly change as a result of the new guidance. The Company adopted this guidance in the first quarter of 2019 using the optional transition method and the package of practical expedients, which allowed for the adoption of the standard as of January 1, 2019, without restating previously disclosed information. Management elected the optional transition method of adoption due to the overall immateriality of the balance sheet gross up in the period of adoption. The package of practical expedients allowed management to not reassess the lease classification for leases, including those that had expired during the periods presented or that still existed at the time of adoption. We have included additional disclosures in the notes to the consolidated financial statements. (See Leases.)
Leases [Policy Text Block]	We determine if a contract is, or contains, a lease at inception and recognize a right-of-use asset and lease liability for all leases with a term greater than 12 months. Our right-of-use assets and lease liabilities for operating leases are included in Other Non-Current Assets, Other Current Liabilities and Other Non-Current Liabilities, respectively, in our Consolidated Balance Sheet. We currently do not have any finance leases. Right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. Operating lease right-of-use assets and lease liabilities are recognized at the commencement date based on the estimated present value of lease payments over the lease term. As our leases do not provide an explicit rate, we determine the present value of future lease payments based on our estimated incremental borrowing rate using information available at the lease commencement date. The operating lease right-of-use asset includes lease payments to be made during the lease term and any lease incentives, as applicable. NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued) Leases (Continued) Our leases may include options to extend or buy out the lease at certain points throughout the term, and if it is reasonably certain that we will exercise that option at lease commencement, we include those rental payments in our calculation of the right-of-use asset and lease liability. Lease and rent expense is recognized on a straight-line basis over the lease term. Leases with a term of 12 months or less are not recognized on the Consolidated Balance Sheet. The majority of our operating leases are for heavy equipment, vehicles and land with fixed monthly payments which we group into two categories: Vehicles and Equipment; and Land and Other. Our largest operating lease is for the dragline at BNI Energy which includes a termination payment at the end of the lease term if we do not exercise our purchase option. The amount of this payment is $3 million and is included in our calculation of the right-of-use asset and lease liability recorded. None of our other leases contain residual value guarantees.
Short-term Leases [Policy Text Block]	Lease and rent expense is recognized on a straight-line basis over the lease term. Leases with a term of 12 months or less are not recognized on the Consolidated Balance Sheet.
CIP Financial Incentives [Policy Text Block]	CIP financial incentives are recognized in the period in which the MPUC approves the filing.
Regulatory Assets and Liabilities [Policy Text Block]	Our regulated utility operations are subject to accounting guidance for the effect of certain types of regulation. Regulatory assets represent incurred costs that have been deferred as they are probable for recovery in customer rates. Regulatory liabilities represent obligations to make refunds to customers and amounts collected in rates for which the related costs have not yet been incurred. The Company assesses quarterly whether regulatory assets and liabilities meet the criteria for probability of future recovery or deferral. With the exception of the regulatory asset for Boswell Units 1 and 2 net plant and equipment, no other regulatory assets are currently earning a return. The recovery, refund or credit to rates for these regulatory assets and liabilities will occur over the periods either specified by the applicable regulatory authority or over the corresponding period related to the asset or liability.
Equity Method Investments [Policy Text Block]	We account for our investment in Nobles 2 under the equity method of accounting.We account for our investment in ATC under the equity method of accounting.
Fair Value Measurement [Policy Text Block]	Non-financial assets such as equity method investments, land inventory, and property, plant and equipment are measured at fair value when there is an indicator of impairment and recorded at fair value only when an impairment is recognized.Each asset and liability is classified based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment, which may affect the valuation of these assets and liabilities and their placement within the fair value hierarchy levels.We utilize market data or assumptions that market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs can be readily observable, market corroborated or generally unobservable. We primarily apply the market approach for recurring fair value measurements and endeavor to utilize the best available information. Accordingly, we utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. These inputs, which are used to measure fair value, are prioritized through the fair value hierarchy.
Power Purchase Agreements [Policy Text Block]	Our long-term PPAs have been evaluated under the accounting guidance for variable interest entities. We have determined that either we have no variable interest in the PPAs or, where we do have variable interests, we are not the primary beneficiary; therefore, consolidation is not required. These conclusions are based on the fact that we do not have both control over activities that are most significant to the entity and an obligation to absorb losses or receive benefits from the entity’s performance. Our financial exposure relating to these PPAs is limited to our capacity and energy payments.
Environmental Accruals [Policy Text Block]	We review environmental matters on a quarterly basis. Accruals for environmental matters are recorded when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated based on current law and existing technologies. Accruals are adjusted as assessment and remediation efforts progress, or as additional technical or legal information becomes available. Accruals for environmental liabilities are included in the Consolidated Balance Sheet at undiscounted amounts and exclude claims for recoveries from insurance or other third parties. Costs related to environmental contamination treatment and cleanup are expensed unless recoverable in rates from customers.
Earnings Per Share [Policy Text Block]	We compute basic earnings per share using the weighted average number of shares of common stock outstanding during each period. The difference between basic and diluted earnings per share, if any, arises from non-vested restricted stock units and performance share awards granted under our Executive Long-Term Incentive Compensation Plan.
Income Tax [Policy Text Block]	The Company's tax provision for interim periods is determined using an estimate of its annual effective tax rate, adjusted for discrete items arising in that quarter. In each quarter, the Company updates its estimate of the annual effective tax rate and if the estimated annual effective tax rate changes, the Company would make a cumulative adjustment in that quarter.
Uncertain Tax Positions [Policy Text Block]	The unrecognized tax benefit amounts have been presented as reductions to the tax benefits associated with NOL and tax credit carryforwards on the Consolidated Balance Sheet.
Business Segments [Policy Text Block]	We present three reportable segments: Regulated Operations, ALLETE Clean Energy and U.S. Water Services. We measure performance of our operations through budgeting and monitoring of contributions to consolidated net income by each business segment.

Operations and Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Cash, Cash Equivalents and Restricted Cash [Table Text Block]

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheet that aggregate to the amounts presented in the Consolidated Statement of Cash Flows.



Cash, Cash Equivalents and Restricted Cash	June 30, 2019		December 31, 2018		June 30, 2018		December 31, 2017
Millions
Cash and Cash Equivalents		$203.1		$69.1		$121.9		$98.9
Restricted Cash included in Prepayments and Other	0.9		1.3		2.3		2.6
Restricted Cash included in Other Non-Current Assets	2.6		8.6		8.6		8.6
Cash, Cash Equivalents and Restricted Cash on the Consolidated Statement of Cash Flows		$206.6		$79.0		$132.8		$110.1

Inventories – Net [Table Text Block]



Inventories – Net	June 30, 2019		December 31, 2018
Millions
Fuel (a)		$33.4		$26.0
Materials and Supplies	44.8		44.2
Raw Materials (b)	—		2.8
Work in Progress (b)	—		6.1
Finished Goods (b)	—		8.4
Reserve for Obsolescence (b)	—		(0.8		)
Total Inventories – Net		$78.2		$86.7


(a)	Fuel consists primarily of coal inventory at Minnesota Power.


(b)	On March 26, 2019, ALLETE completed the sale of U.S. Water Services which resulted in the removal of the related inventory items from the Consolidated Balance Sheet.

Other Non-Current Assets [Table Text Block]



Other Non-Current Assets	June 30, 2019		December 31, 2018
Millions
Contract Assets (a)		$29.2		$30.7
Finance Receivable (b)	—		10.4
Operating Lease Right-of-use Assets (c)	31.2		—
ALLETE Properties	22.6		24.4
Other	80.8		86.9
Total Other Non-Current Assets		$163.8		$152.4


(a)	Contract Assets consist of payments made to customers as an incentive to execute or extend service agreements. The contract payments are being amortized over the term of the respective agreements as a reduction to revenue.


(b)	Finance Receivable related to the 2016 sale of Ormond Crossings and Lake Swamp, which was collected in the second quarter of 2019.


(c)	See Leases.



Other Current Liabilities	June 30, 2019		December 31, 2018
Millions
Provision for Interim Rate Refund (a)	—			$40.0
PSAs		$12.4	12.6
Contract Liabilities (b)	—		7.6
Provision for Tax Reform Refund (c)	0.4		10.7
Contingent Consideration (d)	—		3.8
Operating Lease Liabilities (e)	7.2		—
Other	39.5		53.8
Total Other Current Liabilities		$59.5		$128.5

Other Current Liabilities [Table Text Block]



Other Current Liabilities	June 30, 2019		December 31, 2018
Millions
Provision for Interim Rate Refund (a)	—			$40.0
PSAs		$12.4	12.6
Contract Liabilities (b)	—		7.6
Provision for Tax Reform Refund (c)	0.4		10.7
Contingent Consideration (d)	—		3.8
Operating Lease Liabilities (e)	7.2		—
Other	39.5		53.8
Total Other Current Liabilities		$59.5		$128.5


(a)	Provision for Interim Rate Refund was refunded to Minnesota Power’s retail customers in the second quarter of 2019.


(b)	Contract Liabilities consist of deposits received as a result of entering into contracts with our customers prior to completing our performance obligations.


(c)	Provision for Tax Reform Refund related to the income tax benefits of the TCJA in 2018 was refunded to Minnesota Power customers in the first quarter of 2019 and will be refunded to SWL&P customers in 2019 and 2020.


(d)	Contingent Consideration related to the earnings-based payment resulting from the U.S. Water Services acquisition was paid in the first quarter of 2019.

(e)

See Leases.

Other Non-Current Liabilities [Table Text Block]



Other Non-Current Liabilities	June 30, 2019		December 31, 2018
Millions
Asset Retirement Obligation		$142.7		$138.6
PSAs	70.7		76.9
Operating Lease Liabilities (a)	24.0		—
Other	45.4		47.1
Total Other Non-Current Liabilities		$282.8		$262.6


(a)	See Leases.

Supplemental Statement of Cash Flows Information [Table Text Block]

Supplemental Statement of Cash Flows Information.



Six Months Ended June 30,	2019		2018
Millions
Cash Paid for Interest – Net of Amounts Capitalized		$33.8		$33.0
Noncash Investing and Financing Activities
Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment	$21.1		$(39.4)
Reclassification of Property, Plant and Equipment to Inventory (a)	—			$46.3
Recognition of Right-of-use Assets and Lease Liabilities (b)	$31.2		—
Capitalized Asset Retirement Costs		$1.4		$20.8
AFUDC–Equity		$1.3		$0.5


(a)	In February 2018, Montana-Dakota Utilities exercised its option to purchase the Thunder Spirit II wind energy facility upon completion, resulting in a reclassification from Property, Plant and Equipment – Net to Inventories – Net for project costs incurred in the prior year.


(b)	See Leases.

Lease, Cost [Table Text Block]

Additional information on the components of lease cost and presentation of cash flows were as follows:



	Quarter Ended		Six Months Ended
	June 30,		June 30,
	2019		2019
Millions
Operating Lease Cost		$2.8		$5.7

Other Information:
Operating Cash Flows From Operating Leases		$2.8		$5.7

Additional information related to leases was as follows:



	June 30,
	2019
Millions
Balance Sheet Information Related to Leases:
Other Non-Current Assets		$31.2
Total Operating Lease Right-of-use Assets		$31.2

Other Current Liabilities		$7.2
Other Non-Current Liabilities	24.0
Total Operating Lease Liabilities		$31.2

Weighted Average Remaining Lease Term (Years):
Operating Leases - Vehicles and Equipment	4
Operating Leases - Land and Other	29

Weighted Average Discount Rate:
Operating Leases - Vehicles and Equipment	3.2		%
Operating Leases - Land and Other	4.5		%

Lessee, Operating Lease, Liability, Maturity [Table Text Block]

Maturities of lease liabilities were as follows:



	June 30, 2019
Millions
2019		$4.2
2020	7.9
2021	6.1
2022	4.9
2023	3.1
Thereafter	9.4
Total Lease Payments Due	35.6
Less: Imputed Interest	4.4
Total Lease Obligations	31.2
Less: Current Lease Obligations	7.2
Long-term Lease Obligations		$24.0

Fair Value (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Recurring Fair Value Measures [Table Text Block]



	Fair Value as of June 30, 2019
Recurring Fair Value Measures	Level 1		Level 2		Level 3		Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities		$10.9	—		—			$10.9
Available-for-sale – Corporate and Governmental Debt Securities (b)	—			$9.5	—		9.5
Cash Equivalents	1.1		—		—		1.1
Total Fair Value of Assets		$12.0		$9.5	—			$21.5

Liabilities
Deferred Compensation (c)	—			$21.7	—			$21.7
Total Fair Value of Liabilities	—			$21.7	—			$21.7
Total Net Fair Value of Assets (Liabilities)		$12.0	$(12.2)		—		$(0.2)


	Fair Value as of December 31, 2018
Recurring Fair Value Measures	Level 1		Level 2		Level 3		Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities		$12.2	—		—			$12.2
Available-for-sale – Corporate and Governmental Debt Securities	—			$8.0	—		8.0
Cash Equivalents	1.0		—		—		1.0
Total Fair Value of Assets		$13.2		$8.0	—			$21.2

Liabilities
Deferred Compensation (c)	—			$19.8	—			$19.8
U.S. Water Services Contingent Consideration (d)	—		—			$3.8	3.8
Total Fair Value of Liabilities	—			$19.8		$3.8		$23.6
Total Net Fair Value of Assets (Liabilities)		$13.2	$(11.8)		$(3.8)		$(2.4)


(a)	Included in Other Non-Current Assets on the Consolidated Balance Sheet.


(b)	As of June 30, 2019, the aggregate amount of available-for-sale corporate and governmental debt securities maturing in one year or less was $3.1 million, in one year to less than three years was $3.9 million, in three years to less than five years was $1.6 million and in five or more years was $0.9 million.


(c)	Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.


(d)	Included in Other Current Liabilities on the Consolidated Balance Sheet.

Financial Instruments [Table Text Block]



Financial Instruments	Carrying Amount	Fair Value
Millions
Long-Term Debt, Including Long-Term Debt Due Within One Year
June 30, 2019	$1,543.0	$1,684.3
December 31, 2018	$1,495.2	$1,534.6

Short-Term and Long-Term Debt (Tables)

6 Months Ended

Jun. 30, 2019

Debt Disclosure [Abstract]

Schedule of Short-Term and Long-Term Debt [Table Text Block]

The following tables present the Company’s short-term and long-term debt as of June 30, 2019, and December 31, 2018:



June 30, 2019	Principal		Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt		$28.1	$(0.4)		$27.7
Long-Term Debt	1,514.9		(9.0)	1,505.9
Total Debt		$1,543.0	$(9.4)		$1,533.6



December 31, 2018	Principal		Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt		$57.9	$(0.4)		$57.5
Long-Term Debt	1,437.3		(8.8)	1,428.5
Total Debt		$1,495.2	$(9.2)		$1,486.0

Schedule of Long-term Debt Instruments [Table Text Block]

On March 1, 2019, ALLETE issued and sold the following First Mortgage Bonds (the Bonds):



Maturity Date	Principal Amount	Interest Rate
March 1, 2029	$70 Million	4.08%
March 1, 2049	$30 Million	4.47%

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
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-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Income Tax Expense (Tables)

6 Months Ended

Jun. 30, 2019

Income Tax Disclosure [Abstract]

Income Tax Expense [Table Text Block]



	Quarter Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019			2018
Millions
Current Income Tax Expense (Benefit) (a)
Federal	—		—		—			—
State	$(0.1)		$(0.3)			$0.2			$0.4
Total Current Income Tax Expense (Benefit)	$(0.1)		$(0.3)			$0.2			$0.4
Deferred Income Tax Expense (Benefit)
Federal (b)	$(7.1)		$(7.4)		$(16.8)			$(14.2)
State (c)	2.5		2.4		15.0			5.0
Investment Tax Credit Amortization	(0.1	)	(0.1	)	(0.3		)	(0.3		)
Total Deferred Income Tax Benefit	$(4.7)		$(5.1)		$(2.1)			$(9.5)
Total Income Tax Benefit	$(4.8)		$(5.4)		$(1.9)			$(9.1)

(a)


(b)	For each of the six months ended June 30, 2019, and 2018, the federal income tax benefit is primarily due to production tax credits.


(c)	For the six months ended June 30, 2019, the state income tax expense is primarily due to the sale of U.S. Water Services.

Reconciliation of Taxes from Federal Statutory Rate to Total Income Tax Expense [Table Text Block]



	Quarter Ended						Six Months Ended
Reconciliation of Taxes from Federal Statutory	June 30,						June 30,
Rate to Total Income Tax Expense	2019			2018			2019			2018
Millions
Income Before Income Taxes		$29.4			$25.9			$102.8			$73.2
Statutory Federal Income Tax Rate	21		%	21		%	21		%	21		%
Income Taxes Computed at Statutory Federal Rate		$6.2			$5.4			$21.6			$15.4
Increase (Decrease) in Income Tax Due to:
State Income Taxes – Net of Federal Income Tax Benefit	1.9			1.6			12.0			4.2
Production Tax Credits	(9.8		)	(11.2		)	(26.1		)	(25.6		)
Regulatory Differences – Excess Deferred Tax	(1.6		)	(2.2		)	(4.8		)	(4.4		)
U.S. Water Services Sale of Stock Basis Difference	(0.7		)	—			1.7			—
Share-Based Compensation	—			—			(0.9		)	(0.5		)
Other	(0.8		)	1.0			(5.4		)	1.8
Total Income Tax Benefit	$(4.8)			$(5.4)			$(1.9)			$(9.1)

Business Segments (Tables)

6 Months Ended

Jun. 30, 2019

Segment Reporting [Abstract]

Business Segments [Table Text Block]



	Quarter Ended					Six Months Ended
	June 30,					June 30,
	2019		2018			2019			2018
Millions
Operating Revenue
Regulated Operations
Residential		$29.2		$30.7			$74.4			$71.4
Commercial	34.9		36.2			73.8			72.8
Municipal	12.2		13.7			27.6			27.7
Industrial	120.3		115.3			241.9			230.2
Other Power Suppliers	35.2		42.7			74.6			86.4
Other	18.0		19.2			39.7			39.5
Total Regulated Operations	249.8		257.8			532.0			528.0

Energy Infrastructure and Related Services

ALLETE Clean Energy
Long-term PSA	12.5		12.4			27.1			31.0
Other	2.9		5.9			5.8			11.9
Total ALLETE Clean Energy	15.4		18.3			32.9			42.9

U.S. Water Services (a)
Point-in-Time	—		25.7			19.0			48.0
Contract	—		9.5			9.2			19.0
Capital Project	—		6.3			5.2			12.7
Total U.S. Water Services	—		41.5			33.4			79.7

Corporate and Other
Long-term Contract	21.2		22.7			41.4			42.7
Other	4.0		3.8			7.9			9.0
Total Corporate and Other	25.2		26.5			49.3			51.7
Total Operating Revenue		$290.4		$344.1			$647.6			$702.3
Net Income (Loss)
Regulated Operations		$30.3		$26.0			$81.8			$69.9

Energy Infrastructure and Related Services
ALLETE Clean Energy	1.9		6.8			7.7			14.9
U.S. Water Services (a)	—		0.2			(1.1		)	(1.2		)

Corporate and Other (a)	2.0		(1.7		)	16.3			(1.3		)
Total Net Income		$34.2		$31.3			$104.7			$82.3


(a)	On March 26, 2019, ALLETE completed the sale of U.S. Water Services. The Company recognized a gain on the sale of $11.1 million after-tax reflected in Corporate and Other in 2019. (See Note 1. Operations and Significant Accounting Policies.)



	June 30, 2019		December 31, 2018
Millions
Assets
Regulated Operations		$4,004.4		$3,952.5

Energy Infrastructure and Related Services
ALLETE Clean Energy	755.0		606.6
U.S. Water Services (a)	—		295.8

Corporate and Other	417.1		310.1
Total Assets		$5,176.5		$5,165.0

(a)

On March 26, 2019, ALLETE completed the sale of U.S. Water Services. (See Note 1. Operations and Significant Accounting Policies.)

Operations and Significant Accounting Policies (Details) - USD ($)
$ in Millions

Jun. 30, 2019

Dec. 31, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Cash, Cash Equivalents and Restricted Cash [Abstract]

Cash and Cash Equivalents

$ 203.1

$ 69.1

$ 121.9

$ 98.9

Restricted Cash included in Prepayments and Other

0.9

1.3

2.3

2.6

Restricted Cash included in Other Non-Current Assets

2.6

8.6

Total Cash, Cash Equivalents and Restricted Cash

206.6

79.0

$ 132.8

$ 110.1

Inventories – Net [Abstract]

Fuel

^[1]

33.4

26.0

Materials and Supplies

44.8

44.2

Raw Materials (b)

^[2]

0.0

2.8

Work in Progress (b)

^[2]

0.0

6.1

Finished Goods (b)

^[2]

0.0

8.4

Reserve for Obsolescence (b)

^[2]

0.0

(0.8)

Total Inventories – Net

78.2

86.7

Other Non-Current Assets [Abstract]

Contract Assets

^[3]

29.2

30.7

Finance Receivable

^[4]

0.0

10.4

Operating Lease, Right-of-Use Asset

^[5]

31.2

0.0

ALLETE Properties

22.6

24.4

Other

80.8

86.9

Total Other Non-Current Assets

163.8

152.4

Other Current Liabilites [Abstract]

Provision for Interim Rate Refund

^[6]

0.0

40.0

PSAs

12.4

12.6

Contract Liabilities

^[7]

0.0

7.6

Provision for Tax Reform Refunds

^[8]

0.4

10.7

Contingent Consideration

^[9]

0.0

3.8

Operating Lease Liabilities

^[10]

7.2

0.0

Other

39.5

53.8

Total Other Current Liabilities

59.5

128.5

Other Non-Current Liabilities [Abstract]

Asset Retirement Obligation

142.7

138.6

PSAs

70.7

76.9

Operating Lease Liabilities

24.0

0.0

Other

45.4

47.1

Total Other Non-Current Liabilities

$ 282.8

$ 262.6

[1]	Fuel consists primarily of coal inventory at Minnesota Power.
[2]	On March 26, 2019, ALLETE completed the sale of U.S. Water Services which resulted in the removal of the related inventory items from the Consolidated Balance Sheet.
[3]	Contract Assets consist of payments made to customers as an incentive to execute or extend service agreements. The contract payments are being amortized over the term of the respective agreements as a reduction to revenue.
[4]	Finance Receivable related to the 2016 sale of Ormond Crossings and Lake Swamp, which was collected in the second quarter of 2019.
[5]	See Leases.
[6]	Provision for Interim Rate Refund was refunded to Minnesota Power’s retail customers in the second quarter of 2019
[7]	Contract Liabilities consist of deposits received as a result of entering into contracts with our customers prior to completing our performance obligations.
[8]	Provision for Tax Reform Refund related to the income tax benefits of the TCJA in 2018 was refunded to Minnesota Power customers in the first quarter of 2019 and will be refunded to SWL&P customers in 2019 and 2020.
[9]	Contingent Consideration related to the earnings-based payment resulting from the U.S. Water Services acquisition was paid in the first quarter of 2019.
[10]	See Leases.

Operations and Significant Accounting Policies - Supplemental Statement of Cash Flows Information (Details) - USD ($)
$ in Millions

6 Months Ended

Jun. 30, 2019

Jun. 30, 2018

Supplemental Cash Flow Information [Abstract]

Cash Paid for Interest – Net of Amounts Capitalized

$ 33.8

$ 33.0

Noncash Investing and Financing Activities [Abstract]

Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment

21.1

(39.4)

Reclassification of Property, Plant and Equipment to Inventory

^[1]

0.0

46.3

Recognition of Right-of-use Assets and Lease Liabilities

^[2]

31.2

0.0

Capitalized Asset Retirement Costs

1.4

20.8

AFUDC–Equity

$ 1.3

$ 0.5

[1]	In February 2018, Montana-Dakota Utilities exercised its option to purchase the Thunder Spirit II wind energy facility upon completion, resulting in a reclassification from Property, Plant and Equipment – Net to Inventories – Net for project costs incurred in the prior year.
[2]	See Leases.

Operations and Significant Accounting Policies - Leases (Details) - USD ($)
$ in Millions

3 Months Ended

6 Months Ended

Jun. 30, 2019

Dec. 31, 2018

Lessee Disclosure [Abstract]

Operating Lease Residual Value Guarantee

Our largest operating lease is for the dragline at BNI Energy which includes a termination payment at the end of the lease term if we do not exercise our purchase option.

Residual Value Guarantee

$ 3.0

Operating Lease Cost [Abstract]

Operating Lease Cost

2.8

5.7

Other Information [Abstract]

Operating Cash Flows from Operating Leases

2.8

5.7

Balance Sheet Information Related to Leases [Abstract]

Operating Lease, Right-of-Use Asset

^[1]

$ 31.2

$ 0.0

Other Non-Current Assets

us-gaap:OperatingLeaseRightOfUseAsset

Total Lease Obligations

$ 31.2

Operating Lease Liabilities

^[2]

$ 7.2

0.0

Other Current Liabilities

us-gaap:OperatingLeaseLiabilityCurrent

Operating Lease Liabilities

$ 24.0

$ 0.0

Other Non-Current Liabilities

us-gaap:OperatingLeaseLiabilityNoncurrent

Vehicles and Equipment [Member]

Lease Description [Line Items]

Weighted Average Remaining Lease Term

4 years

Weighted Average Discount Rate

3.20%

Land and Other [Member]

Lease Description [Line Items]

Weighted Average Remaining Lease Term

29 years

Weighted Average Discount Rate

4.50%

[1]	See Leases.
[2]	See Leases.

Operations and Significant Accounting Policies - Lease Maturities (Details) - USD ($)
$ in Millions

Jun. 30, 2019

Dec. 31, 2018

Lessee, Operating Lease, Liability, Payment, Due [Abstract]

$ 4.2

7.9

6.1

4.9

3.1

9.4

Total Lease Payments Due

35.6

Less: Imputed Interest

4.4

Total Lease Obligations

31.2

Operating Lease Liabilities

^[1]

$ 7.2

$ 0.0

Other Current Liabilities

us-gaap:OperatingLeaseLiabilityCurrent

Operating Lease Liabilities

$ 24.0

0.0

Other Non-Current Liabilities

us-gaap:OperatingLeaseLiabilityNoncurrent

Less: Current Lease Obligations

^[1]

$ 7.2

0.0

Long-term Lease Obligations

$ 24.0

$ 0.0

[1]	See Leases.

Regulatory Matters - Electric Rates (Details) - Retail Customers [Member] - USD ($) $ in Millions			6 Months Ended
	Dec. 20, 2018	Jan. 18, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
PSCW [Member] \| 2018 Wisconsin General Rate Case [Member] \| SWL&P [Member]
Regulatory Matters [Line Items]
Approved Return on Common Equity	10.40%
Approved Equity Ratio	55.00%
Approved Rate Increase Amount	$ 1.3
Electric Rates [Member] \| MPUC [Member] \| Minnesota Cost Recovery Riders [Member] \| Minnesota Power [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders			$ 17.4	$ 52.1
Electric Rates [Member] \| MPUC [Member] \| 2016 Minnesota General Rate Case [Member] \| Minnesota Power [Member]
Regulatory Matters [Line Items]
Approved Return on Common Equity		9.25%
Approved Equity Ratio		53.81%
Annual Additional Revenue Generated from Requested Final Rate Increase		$ 13.0
Reserve for Interim Rate Refund					$ 40.0

Regulatory Matters - Integrated Resource Plan (Details) - MPUC [Member] - Resource Package [Member]	Jul. 28, 2017 MW
Natural Gas-fired [Member] \| Combined-Cycle Natural Gas-Fired Generating Facility [Member] \| Minimum [Member] \| Jointly Owned by ALLETE and Dairyland Power Cooperative [Member] \| Natural Gas PPA [Member] \| Jointly Owned Electricity Generation Plant [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Jointly Owned (MW)	525
Natural Gas-fired [Member] \| Combined-Cycle Natural Gas-Fired Generating Facility [Member] \| Maximum [Member] \| Jointly Owned by ALLETE and Dairyland Power Cooperative [Member] \| Natural Gas PPA [Member] \| Jointly Owned Electricity Generation Plant [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Jointly Owned (MW)	550
Minnesota Power [Member] \| Natural Gas PPA [Member]
Regulatory Matters [Line Items]
Output Being Purchased (MW)	250
Minnesota Power [Member] \| Natural Gas-fired [Member] \| Natural Gas PPA [Member]
Regulatory Matters [Line Items]
Expected Output Entitlement (Percent)	50.00%
Minnesota Power [Member] \| Wind Turbine Generators [Member] \| Nobles 2 [Member] \| Nobles 2 [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Counterparty Owned (MW)	250
Minnesota Power [Member] \| Solar Energy Generation [Member] \| Solar Energy PPA [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Counterparty Owned (MW)	10

Regulatory Matters - Regulatory Assets and Liabilities (Details) - USD ($)
$ in Millions

6 Months Ended

Jun. 30, 2019

Dec. 31, 2018

Regulatory Assets and Liabilities [Line Items]

Regulatory Assets Currently Earning a Return

With the exception of the regulatory asset for Boswell Units 1 and 2 net plant and equipment, no other regulatory assets are currently earning a return.

Non-Current Regulatory Assets

$ 391.2

$ 389.5

Current Regulatory Liabilities

^[1]

3.5

55.1

Non-Current Regulatory Liabilities

508.8

512.1

Total Regulatory Liabilities

512.3

567.2

Provision for Interim Rate Refund [Domain]

Regulatory Assets and Liabilities [Line Items]

Current Regulatory Liabilities

^[1],[2]

0.0

40.0

Transmission Formula Rates [Member]

Regulatory Assets and Liabilities [Line Items]

Current Regulatory Liabilities

^[1]

3.1

4.4

Non-Current Regulatory Liabilities

0.8

1.6

Provision for Tax Reform Refund [Domain]

Regulatory Assets and Liabilities [Line Items]

Current Regulatory Liabilities

^[1],[3]

0.4

10.7

Income Taxes [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

386.2

396.4

Wholesale and Retail Contra AFUDC [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

70.6

64.4

Plant Removal Obligations [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

29.3

25.1

North Dakota Investment Tax Credits [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

12.3

14.7

CIP Financial Incentive [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

7.0

1.5

Cost Recovery Riders [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

0.0

6.9

Other

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

2.6

1.5

Defined Benefit Pension and Other Postretirement Benefit Plans [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

216.5

218.5

Income Taxes [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

102.2

105.5

Asset Retirement Obligations [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

32.3

32.6

Boswell 1 & 2 [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

13.5

16.3

Cost Recovery Riders [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

10.0

0.0

Manufactured Gas Plant [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

8.1

8.0

PPACA Income Tax Deferral [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

4.9

5.0

Other

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

$ 3.7

$ 3.6

[1]	Current regulatory liabilities are presented within Other Current Liabilities on the Consolidated Balance Sheet.
[2]	This amount was refunded to Minnesota Power’s regulated retail customers in the second quarter of 2019.
[3]	Provision for Tax Reform Refund related to the income tax benefits of the TCJA in 2018 was refunded to Minnesota Power customers in the first quarter of 2019 and will be refunded to SWL&P customers in 2019 and 2020.

Equity Investments - Investment in ATC (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
ALLETE's Investment in ATC [Roll Forward]
Equity Investment Balance as of December 31, 2018				$ 161.1
Cash Investments				4.6	$ 3.9
Equity in ATC Earnings		$ 4.8	$ 4.3	10.4	$ 9.0
Equity Investment Balance as of June 30, 2019		$ 160.2		$ 160.2
FERC [Member] \| Return on Equity Complaint [Member]
ALLETE's Investment in ATC [Roll Forward]
Proposed Return on Equity		9.70%		9.70%
Proposed Return on Equity, Including Incentive Adder		10.20%		10.20%
ATC [Member]
Investment in ATC [Line Items]
Ownership Percentage		8.00%		8.00%
Expected Additional Investment in 2019		$ 4.0		$ 4.0
ALLETE's Investment in ATC [Roll Forward]
Equity Investment Balance as of December 31, 2018				128.1
Cash Investments				2.7
Equity in ATC Earnings				10.4
Distributed ATC Earnings				(8.2)
Amortization of the Remeasurement of Deferred Income Taxes				0.6
Equity Investment Balance as of June 30, 2019		$ 133.6		$ 133.6
Authorized Return on Equity				10.32%
Authorized Return on Equity, Including Incentive Adder		10.82%		10.82%
ATC [Member] \| Subsequent Event [Member]
ALLETE's Investment in ATC [Roll Forward]
Cash Investments	$ 1.9

Equity Investments - Investment in Nobles 2 (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($) MW	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investment in Nobles 2 [Line Items]
Equity Method Investment Balance	$ 160.2		$ 161.1
Return of Capital From Equity Investments	$ 8.3	$ 0.0
Nobles 2 [Member]
Investment in Nobles 2 [Line Items]
Ownership Percentage	49.00%
Equity Method Investment Balance	$ 26.6		$ 33.0
Return of Capital From Equity Investments	8.3
Expected Additional Investment in 2019	$ 33.0
Wind Turbine Generators [Member] \| Resource Package [Member] \| Tenaska [Member] \| MPUC [Member] \| Minnesota Power [Member] \| Tenaska PPA [Member]
Investment in Nobles 2 [Line Items]
Generating Capacity Counterparty Owned (MW) \| MW	250
Long-term Contract for Purchase of Electric Power, Term of Contract (Years)	20 years

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($)
$ in Millions

6 Months Ended

Jun. 30, 2019

Jun. 30, 2018

Definite-Lived Intangible Assets [Roll Forward]

Beginning Balance

$ 58.2

Amortization

(1.4)

$ (2.7)

Other Changes

^[1]

55.7

Ending Balance

1.1

Intangible Assets [Abstract]

Total Intangible Assets - Beginning Balance

74.8

Total Intangible Assets - Amortization

(1.4)

$ (2.7)

Total Intangible Assets - Other Changes

^[1]

72.3

Total Intangible Assets - Ending Balance

1.1

Trademarks and Trade Names [Member]

Indefinite-Lived Intangible Assets [Roll Forward]

Beginning Balance

16.6

Other Changes

^[1]

16.6

Ending Balance

0.0

Customer Relationships [Member]

Definite-Lived Intangible Assets [Roll Forward]

Beginning Balance

50.7

Amortization

(1.1)

Other Changes

^[1]

49.6

Ending Balance

0.0

Intangible Assets [Abstract]

Total Intangible Assets - Amortization

(1.1)

Developed Technology and Other [Member]

Definite-Lived Intangible Assets [Roll Forward]

Beginning Balance

^[2]

7.5

Amortization

^[2]

(0.3)

Other Changes

^[1],[2]

6.1

Ending Balance

^[2]

1.1

Intangible Assets [Abstract]

Total Intangible Assets - Amortization

^[2]

$ (0.3)

[1]	On March 26, 2019, ALLETE completed the sale of U.S. Water Services which resulted in the removal of the related intangible assets from the Consolidated Balance Sheet.
[2]	Developed Technology and Other includes patents, non-compete agreements, land easements and trade names with finite lives.

Fair Value - Recurring Fair Value Measures (Details) - USD ($)
$ in Millions

6 Months Ended

Jun. 30, 2019

Dec. 31, 2018

Investments [Abstract]

Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value

$ 3.1

Available-for-sale Securities, Debt Maturities, After One Year Through Three Years, Fair Value

3.9

Available-for-sale Securities, Debt Maturities, After Three Years Through Five Years, Fair Value

1.6

Available-for-sale Securities, Debt Maturities, After Five Years, Fair Value

0.9

Recurring Fair Value Measures [Member]

Investments [Abstract]

Available-for-sale – Equity Securities

^[1]

10.9

$ 12.2

Available-for-sale – Corporate and Governmental Debt Securities (b)

^[1]

9.5

^[2]

8.0

Cash Equivalents

^[1]

1.1

1.0

Total Fair Value of Assets

21.5

21.2

Liabilities [Abstract]

Deferred Compensation

^[3]

21.7

19.8

U.S. Water Services Contingent Consideration

^[4]

3.8

Total Fair Value of Liabilities

21.7

23.6

Total Net Fair Value of Assets (Liabilities)

(0.2)

(2.4)

Recurring Fair Value Measures [Member] | Level 1 [Member]

Investments [Abstract]

Available-for-sale – Equity Securities

^[1]

10.9

12.2

Available-for-sale – Corporate and Governmental Debt Securities (b)

^[1]

0.0

^[2]

0.0

Cash Equivalents

^[1]

1.1

1.0

Total Fair Value of Assets

12.0

13.2

Liabilities [Abstract]

Deferred Compensation

^[3]

0.0

U.S. Water Services Contingent Consideration

^[4]

0.0

Total Fair Value of Liabilities

0.0

Total Net Fair Value of Assets (Liabilities)

12.0

13.2

Recurring Fair Value Measures [Member] | Level 2 [Member]

Investments [Abstract]

Available-for-sale – Equity Securities

^[1]

0.0

Available-for-sale – Corporate and Governmental Debt Securities (b)

^[1]

9.5

^[2]

8.0

Cash Equivalents

^[1]

0.0

Total Fair Value of Assets

9.5

8.0

Liabilities [Abstract]

Deferred Compensation

^[3]

21.7

19.8

U.S. Water Services Contingent Consideration

^[4]

0.0

Total Fair Value of Liabilities

21.7

19.8

Total Net Fair Value of Assets (Liabilities)

(12.2)

(11.8)

Recurring Fair Value Measures [Member] | Level 3 [Member]

Investments [Abstract]

Available-for-sale – Equity Securities

^[1]

0.0

Available-for-sale – Corporate and Governmental Debt Securities (b)

^[1]

0.0

^[2]

0.0

Cash Equivalents

^[1]

0.0

Total Fair Value of Assets

0.0

Liabilities [Abstract]

Deferred Compensation

^[3]

0.0

U.S. Water Services Contingent Consideration

^[4]

3.8

Total Fair Value of Liabilities

0.0

3.8

Total Net Fair Value of Assets (Liabilities)

0.0

$ (3.8)

Recurring Fair Value Measures [Member] | Level 3 [Member] | Payments [Member]

Liabilities [Abstract]

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)

$ 3.8

[1]	Included in Other Non-Current Assets on the Consolidated Balance Sheet.
[2]	As of June 30, 2019, the aggregate amount of available-for-sale corporate and governmental debt securities maturing in one year or less was $3.1 million, in one year to less than three years was $3.9 million, in three years to less than five years was $1.6 million and in five or more years was $0.9 million.
[3]	Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.
[4]	Included in Other Current Liabilities on the Consolidated Balance Sheet.

Fair Value - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fair Value of Financial Instruments [Line Items]
Long-Term Debt, Including Long-Term Debt Due Within One Year - Carrying Amount	$ 1,543.0	$ 1,495.2
Level 2 [Member]
Fair Value of Financial Instruments [Line Items]
Long-Term Debt, Including Long-Term Debt Due Within One Year - Fair Value	$ 1,684.3	$ 1,534.6

Short-Term and Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 01, 2019	Jun. 30, 2019	Jan. 10, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Short-Term Debt - Principal		$ 28.1		$ 57.9
Short-Term Debt - Unamortized Debt Issuance Costs		(0.4)		(0.4)
Short-Term Debt - Total		27.7		57.5
Long-Term Debt - Principal		1,514.9		1,437.3
Long-Term Debt - Unamortized Debt Issuance Costs		(9.0)		(8.8)
Long-Term Debt - Total		1,505.9		1,428.5
Total Debt - Principal		1,543.0		1,495.2
Total Debt - Unamortized Debt Issuance Costs		(9.4)		(9.2)
Total Debt - Total		1,533.6		1,486.0
Letters of Credit Outstanding, Amount		56.3		18.4
Line of Credit, Current		$ 0.0		$ 0.0
ALLETE Bonds 4.08% Due March 2029 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of First Mortgage Bond	$ 70.0
Interest Rate	4.08%
ALLETE Bonds 4.47% Due March 2049 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of First Mortgage Bond	$ 30.0
Interest Rate	4.47%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 400.0
Line of Credit Facility Additional Borrowing Capacity			150.0
Letters of Credit Maximum Issuances			$ 100.0

Commitments, Guarantees and Contingencies - Power Purchase Agreements (Details) - Square Butte PPA [Member] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Square Butte [Member]
Power Purchase Agreements [Line Items]
PPA Counterparty Total Debt Outstanding	$ 301.9
Square Butte [Member] \| Minnesota Power [Member]
Power Purchase Agreements [Line Items]
Cost of Power Purchased	41.1	$ 37.7
Pro Rata Share of PPA Counterparty Interest Expense	$ 4.2	$ 4.6
Square Butte [Member] \| Minnesota Power [Member] \| Square Butte Coal-fired Unit [Member]
Power Purchase Agreements [Line Items]
Expected Output Entitlement	50.00%
Minnkota Power [Member] \| Minnesota Power [Member] \| Square Butte Coal-fired Unit [Member] \| Minnkota Power PSA [Member]
Power Purchase Agreements [Line Items]
Expected Output Entitlement	28.00%	28.00%

Commitments, Guarantees and Contingencies - Transmission (Details) $ in Millions	Jun. 30, 2019 USD ($) kV Miles MW
Great Northern Transmission Line [Member]
Transmission [Line Items]
Total Project Cost in the U.S.	$ 750.0
Total Project Costs Incurred to Date	510.8
Manitoba Hydro [Member] \| Great Northern Transmission Line [Member]
Transmission [Line Items]
Project Costs Recovered from Counterparty	$ 272.7
Minnesota Power [Member] \| Great Northern Transmission Line [Member]
Transmission [Line Items]
Transmission Line Length (Miles) \| Miles	220
Transmission Line Capacity (kV) \| kV	500
Total Project Cost in the U.S.	$ 345.0
Manitoba Hydro PPA [Member] \| Manitoba Hydro [Member]
Transmission [Line Items]
Output Being Purchased (MW) \| MW	250

Commitments, Guarantees and Contingencies - Environmental Matters (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Coal Combustion Residuals [Member] \| Minnesota Power [Member]
Environmental Matters [Line Items]
Expected Period for Costs of Compliance	15 years
Coal Combustion Residuals [Member] \| Minimum [Member] \| Minnesota Power [Member]
Environmental Matters [Line Items]
Estimated Costs of Compliance	$ 65
Coal Combustion Residuals [Member] \| Maximum [Member] \| Minnesota Power [Member]
Environmental Matters [Line Items]
Estimated Costs of Compliance	120
Manufactured Gas Plant [Member] \| SWL&P [Member] \| Superior, WI [Member]
Environmental Matters [Line Items]
Estimated Costs of Compliance (Accrued)	$ 7	$ 7

Commitments, Guarantees and Contingencies - Other Matters (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
ALLETE Clean Energy [Member] \| Letters of Credit [Member]
Guarantor Obligations [Line Items]
Collateral	$ 58.4
BNI Energy Reclamation Liability [Member]
Guarantor Obligations [Line Items]
Estimated Obligation	65.8
BNI Energy Reclamation Liability [Member] \| Surety Bonds [Member]
Guarantor Obligations [Line Items]
Collateral	66.5
ALLETE Properties Development and Maintenance Obligations [Member]
Guarantor Obligations [Line Items]
Estimated Obligation	6.1
ALLETE Properties Development and Maintenance Obligations [Member] \| Surety Bonds and Letters of Credit [Member]
Guarantor Obligations [Line Items]
Collateral	$ 8.6
Town Center District Capital Improvement Bonds [Member]
Guarantor Obligations [Line Items]
Ownership Percentage of Benefited Property	66.00%	68.00%
Annual Assessment	$ 1.4
Palm Coast Park District Special Assessment Bonds [Member]
Guarantor Obligations [Line Items]
Ownership Percentage of Benefited Property	12.00%	19.00%
Annual Assessment	$ 0.6

Earnings Per Share and Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share - Basic [Abstract]
Net Income	$ 34.2	$ 31.3	$ 104.7	$ 82.3
Average Common Shares	51.6	51.3	51.6	51.2
Earnings Per Share	$ 0.66	$ 0.61	$ 2.03	$ 1.61
Earnings Per Share - Diluted [Abstract]
Net Income	$ 34.2	$ 31.3	$ 104.7	$ 82.3
Average Common Shares	51.7	51.5	51.7	51.4
Earnings Per Share	$ 0.66	$ 0.61	$ 2.02	$ 1.60
Dilutive Securities (Shares)	0.1	0.2	0.1	0.2

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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-Name Accounting Standards Codification
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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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-Name Accounting Standards Codification
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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Income Tax Expense (Details) - USD ($)
$ in Millions

3 Months Ended

6 Months Ended

Jun. 30, 2019

Jun. 30, 2018

Jun. 30, 2019

Jun. 30, 2018

Dec. 31, 2018

Current Income Tax Expense (Benefit) [Abstract]

Federal

^[1]

$ 0.0

State

^[1]

(0.1)

(0.3)

0.2

0.4

Total Current Income Tax Expense

(0.1)

(0.3)

0.2

0.4

Deferred Income Tax Expense (Benefit) [Abstract]

Federal

^[2]

(7.1)

(7.4)

(16.8)

(14.2)

State

2.5

2.4

15.0

^[3]

5.0

^[3]

Investment Tax Credit Amortization

(0.1)

(0.3)

Total Deferred Income Tax Expense (Benefit)

(4.7)

(5.1)

(2.1)

(9.5)

Total Income Tax Expense (Benefit)

(4.8)

(5.4)

(1.9)

(9.1)

Reconciliation of Taxes from Federal Statutory Rate to Total Income Tax Expense [Abstract]

Income Before Income Taxes

$ 29.4

$ 25.9

$ 102.8

$ 73.2

Statutory Federal Income Tax Rate

21.00%

Income Taxes Computed at Statutory Federal Rate

$ 6.2

$ 5.4

$ 21.6

$ 15.4

Increase (Decrease) in Income Tax Due to: [Abstract]

State Income Taxes – Net of Federal Income Tax Benefit

1.9

1.6

12.0

4.2

Production Tax Credits

(9.8)

(11.2)

(26.1)

(25.6)

Regulatory Differences – Excess Deferred Tax

(1.6)

(2.2)

(4.8)

(4.4)

U.S. Water Services Sale of Stock Basis Difference

(0.7)

0.0

1.7

0.0

Share-Based Compensation

0.0

(0.9)

(0.5)

Other

(0.8)

1.0

(5.4)

1.8

Total Income Tax Expense (Benefit)

(4.8)

$ (5.4)

$ (1.9)

$ (9.1)

Effective Tax Rate

1.80%

12.40%

Uncertain Tax Positions [Abstract]

Gross Unrecognized Tax Benefits

1.3

$ 1.3

$ 1.6

Gross Unrecognized Tax Benefits That Would Favorably Impact Effective Income Tax Rate

$ 0.6

[1]	For each of the six months ended June 30, 2019, and 2018, the federal and state current tax expense was minimal due to NOLs which resulted from the bonus depreciation provisions of the Protecting Americans from Tax Hikes Act of 2015, the Tax Increase Prevention Act of 2014 and the American Taxpayer Relief Act of 2012. Federal and state NOLs are being carried forward to offset current and future taxable income.
[2]	For each of the six months ended June 30, 2019, and 2018, the federal income tax benefit is primarily due to production tax credits.
[3]	For the six months ended June 30, 2019, the state income tax expense is primarily due to the sale of U.S. Water Services.

Pension and Other Postretirement Benefit Plans (Details) - USD ($)
$ in Millions

3 Months Ended

6 Months Ended

Jun. 30, 2019

Jun. 30, 2018

Jun. 30, 2019

Jun. 30, 2018

Pension [Member]

Components of Net Periodic Benefit Cost (Income) [Abstract]

Service Cost

$ 2.4

$ 2.8

$ 4.7

$ 5.5

Interest Cost

^[1]

8.0

7.4

16.0

14.8

Expected Return on Plan Assets

^[1]

(11.1)

(22.1)

Amortization of Prior Service Credits

^[1]

(0.1)

0.0

(0.1)

0.0

Amortization of Net Loss

^[1]

1.9

3.0

3.7

6.0

Net Periodic Benefit Cost

1.1

2.1

2.2

4.2

Employer Contributions to Defined Benefit Plans

10.4

15.0

Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year

0.0

Operations and Significant Accounting Policies - Sale of U.S. Water Services (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Business Segments [Line Items]
Approximate Gain on Sale of U.S. Water Services, After-tax	$ 11.1
U.S. Water Services [Member]
Business Segments [Line Items]
Cash Purchase Price	270.0
Proceeds from Sale of U.S. Water Services - Net of Transaction Costs and Cash Retained	265.0
Approximate Gain on Sale of U.S. Water Services, After-tax	$ 11.1

Operations and Significant Accounting Policies - ALLETE Clean Energy Asset Acquisition (Details)	May 03, 2019 MW
ALLETE Clean Energy [Member]
Business Segments [Line Items]
Generating Capacity Owned (MW)	300

Regulatory Matters - Conservation Improvement Program (CIP) (Details) - CIP Consolidated Filing [Member] - MPUC [Member] - Minnesota Power [Member] - USD ($) $ in Millions		6 Months Ended
	Jul. 19, 2019	Jun. 30, 2018
Regulatory Matters [Line Items]
CIP Financial Incentive		$ 3.0
Subsequent Event [Member]
Regulatory Matters [Line Items]
CIP Financial Incentive	$ 2.8

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 0.0	$ 148.5

Short-Term and Long-Term Debt - Financial Covenants (Details)	Jun. 30, 2019
Debt Instrument [Line Items]
Actual Ratio of Indebtedness to Total Capitalization	0.42
Maximum [Member]
Debt Instrument [Line Items]
Required Ratio of Indebtedness to Total Capitalization	0.65