0000066756-21-000041 | 10-Q | XBRL Viewer

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Document and Entity Information Document	3 Months Ended
Document and Entity Information Document	Mar. 31, 2021 shares
Document and Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
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	52,188,909
Entity Central Index Key	0000066756
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Balance Sheet - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Current Assets [Abstract]
Cash and Cash Equivalents	$ 159.0	$ 44.3
Accounts Receivable (Less Allowance of $2.6 and $2.5)	113.5	111.9
Inventories – Net	74.0	74.2
Prepayments and Other	31.9	24.5
Total Current Assets	378.4	254.9
Property, Plant and Equipment – Net	4,930.6	4,840.8
Regulatory Assets	472.7	480.9
Equity Investments	301.5	301.2
Other Non-Current Assets	191.3	206.8
Total Assets	6,274.5	6,084.6
Current Liabilities [Abstract]
Accounts Payable	107.0	110.0
Accrued Taxes	75.2	59.4
Accrued Interest	15.3	19.8
Long-Term Debt Due Within One Year	298.5	203.7
Other	78.9	66.7
Total Current Liabilities	574.9	459.6
Long-Term Debt	1,652.4	1,593.2
Deferred Income Taxes	190.2	195.7
Regulatory Liabilities	517.9	524.8
Defined Benefit Pension and Other Postretirement Benefit Plans	212.5	225.8
Other Non-Current Liabilities	280.2	285.3
Total Liabilities	3,428.1	3,284.4
Commitments, Guarantees and Contingencies (Note 6)
Equity [Abstract]
Common Stock Without Par Value, 80.0 Shares Authorized, 52.2 and 52.1 Shares Issued and Outstanding	1,467.6	1,460.9
Accumulated Other Comprehensive Loss	(30.7)	(31.1)
Retained Earnings	883.8	864.8
Total ALLETE Equity	2,320.7	2,294.6
Non-Controlling Interest in Subsidiaries	525.7	505.6
Total Equity	2,846.4	2,800.2
Total Liabilities and Equity	$ 6,274.5	$ 6,084.6

Consolidated Balance Sheet Parentheticals - USD ($) shares in Millions, $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accounts Receivable [Abstract]
Accounts Receivable, Allowance	$ 2.6	$ 2.5
Common Stock [Abstract]
Common Stock, Par Value	$ 0	$ 0
Common Stock, Shares Authorized	80.0	80.0
Common Stock, Shares Outstanding	52.2	52.1
Common Stock, Shares Issued	52.2	52.1

Consolidated Statement of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Revenues [Abstract]
Contracts with Customers - Utility	$ 293.0	$ 265.3
Contracts with Customers - Non-utility	43.4	43.5
Other - Non-utility	2.8	2.8
Total Operating Revenue	339.2	311.6
Operating Expenses [Abstract]
Fuel, Purchased Power and Gas - Utility	120.4	89.0
Transmission Services - Utility	17.7	18.5
Cost of Sales - Non-utility	16.8	16.9
Operating and Maintenance	66.3	61.0
Depreciation and Amortization	58.0	53.4
Taxes Other than Income Taxes	18.0	12.6
Total Operating Expenses	297.2	251.4
Operating Income	42.0	60.2
Other Income (Expense) [Abstract]
Interest Expense	(17.1)	(15.7)
Equity Earnings	4.8	5.2
Other	3.3	1.0
Total Other Expense	(9.0)	(9.5)
Income Before Income Taxes	33.0	50.7
Income Tax Benefit	(10.4)	(13.8)
Net Income	43.4	64.5
Net Loss Attributable to Non-Controlling Interest	(8.4)	(1.8)
Net Income Attributable to ALLETE	$ 51.8	$ 66.3
Earnings Per Share [Abstract]
Basic (Shares)	52.1	51.7
Diluted (Shares)	52.2	51.8
Basic Earnings Per Share of Common Stock	$ 0.99	$ 1.28
Diluted Earnings Per Share of Common Stock	$ 0.99	$ 1.28

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Comprehensive Income [Abstract]
Net Income	$ 43.4	$ 64.5
Other Comprehensive Income (Loss) [Abstract]
Unrealized Loss on Securities Net of Income Tax Benefit of $– and $(0.1)	0.0	(0.4)
Defined Benefit Pension and Other Postretirement Benefit Plans Net of Income Tax Expense of $0.1 and $0.1	0.4	0.2
Total Other Comprehensive Income (Loss)	0.4	(0.2)
Total Comprehensive Income	43.8	64.3
Net Loss Attributable to Non-Controlling Interest	(8.4)	(1.8)
Total Comprehensive Income Attributable to ALLETE	$ 52.2	$ 66.1

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

+ Details

- 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

Consolidated Statement of Comprehensive Income Parentheticals - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Unrealized Gain (Loss) on Securities, Income Tax Expense	$ 0.0	$ (0.1)
Defined Benefit Pension and Other Postretirement Benefit Plans, Income Tax Expense	$ 0.1	$ 0.1

Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities [Abstract]
Net Income	$ 43.4	$ 64.5
AFUDC – Equity	(0.5)	(0.5)
Income from Equity Investments – Net of Dividends	1.0	0.0
Realized and Unrealized (Gain) Loss on Investments and Property, Plant and Equipment	(0.5)	3.1
Depreciation Expense	58.0	53.4
Amortization of PSAs	(2.8)	(2.8)
Amortization of Other Intangible Assets and Other Assets	2.5	2.3
Deferred Income Tax Benefit	(10.4)	(13.8)
Share-Based and ESOP Compensation Expense	1.7	1.7
Defined Benefit Pension and Postretirement Benefit Expense	1.1	0.0
Bad Debt Expense	0.4	0.4
Changes in Operating Assets and Liabilities [Abstract]
Accounts Receivable	(2.2)	(3.4)
Inventories	0.2	(6.2)
Prepayments and Other	(1.3)	4.0
Accounts Payable	(8.6)	(5.5)
Other Current Liabilities	23.5	7.1
Cash Contributions to Defined Benefit Pension Plans	(10.3)	(10.7)
Changes in Regulatory and Other Non-Current Assets	(0.6)	(11.4)
Changes in Regulatory and Other Non-Current Liabilities	(6.1)	6.0
Cash from Operating Activities	88.5	88.2
Investing Activities [Abstract]
Proceeds from Sale of Available-for-sale Securities	1.2	0.9
Payments for Purchase of Available-for-sale Securities	(0.6)	(1.1)
Payments for Equity Investments	(1.0)	(27.8)
Additions to Property, Plant and Equipment	(134.4)	(154.3)
Other Investing Activities	3.9	0.4
Cash for Investing Activities	(130.9)	(181.9)
Financing Activities [Abstract]
Proceeds from Issuance of Common Stock	5.0	3.3
Proceeds from Issuance of Short-Term and Long-Term Debt	194.9	110.0
Repayments of Long-Term Debt	(41.4)	(1.4)
Proceeds from Non-controlling Interests	28.9	0.0
Dividends on Common Stock	(32.8)	(31.9)
Other Financing Activities	(0.4)	0.1
Cash from Financing Activities	154.2	80.1
Change in Cash, Cash Equivalents and Restricted Cash	111.8	(13.6)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 177.0	$ 78.9

Consolidated Statement of Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Non-controlling Interest [Member]
Balance, Beginning Balance at Dec. 31, 2019		$ 1,436.7	$ (23.6)	$ 818.8	$ 103.7
Consolidated Statement of Equity [Roll Forward]
Common Stock Issued		5.0
Unrealized Loss on Debt Securities	$ (0.4)		(0.4)
Defined Benefit Pension and Other Postretirement Plans	0.2		0.2
Net Income Attributable ALLETE	66.3			66.3
Common Stock Dividends	31.9			(31.9)
Proceeds from Non-controlling Interests	0.0				0.0
Net Loss Attributable to Non-Controlling Interest	(1.8)				(1.8)
Distributions to Non-controlling Interest					0.0
Balance, End of Period at Mar. 31, 2020	$ 2,373.0	1,441.7	(23.8)	853.2	101.9
Consolidated Statement of Equity [Roll Forward]
Dividends Per Share of Common Stock	$ 0.6175
Balance, Beginning Balance at Dec. 31, 2020	$ 2,800.2	1,460.9	(31.1)	864.8	505.6
Consolidated Statement of Equity [Roll Forward]
Common Stock Issued		6.7
Unrealized Loss on Debt Securities	0.0		0.0
Defined Benefit Pension and Other Postretirement Plans	0.4		0.4
Net Income Attributable ALLETE	51.8			51.8
Common Stock Dividends	32.8			(32.8)
Proceeds from Non-controlling Interests	28.9				28.9
Net Loss Attributable to Non-Controlling Interest	(8.4)				(8.4)
Distributions to Non-controlling Interest					(0.4)
Balance, End of Period at Mar. 31, 2021	$ 2,846.4	$ 1,467.6	$ (30.7)	$ 883.8	$ 525.7
Consolidated Statement of Equity [Roll Forward]
Dividends Per Share of Common Stock	$ 0.63

Operations and Significant Accounting Policies - Supplemental Statement of Cash Flows Information - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Cash Paid for Interest – Net of Amounts Capitalized	$ 21.2	$ 18.3
Noncash Investing and Financing Activities [Abstract]
Increase in Accounts Payable for Capital Additions to Property, Plant and Equipment	5.6	4.7
Capitalized Asset Retirement Costs	3.5	1.6
AFUDC–Equity	$ 0.5	$ 0.5

Operations and Significant Accounting Policies

3 Months Ended

Mar. 31, 2021

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 March 31, 2021, restricted cash amounts included in Prepayments and Other on the Consolidated Balance Sheet include collateral deposits required under an ALLETE Clean Energy loan agreement. The restricted cash amounts included in Other Non-Current Assets represent collateral deposits required under ALLETE Clean Energy loan and tax equity financing agreements as well as PSAs. 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	March 31, 2021	December 31, 2020	March 31, 2020	December 31, 2019
Millions
Cash and Cash Equivalents	$159.0	$44.3	$67.0	$69.3
Restricted Cash included in Prepayments and Other	7.1	0.8	6.1	2.8
Restricted Cash included in Other Non-Current Assets	10.9	20.1	5.8	20.4
Cash, Cash Equivalents and Restricted Cash on the Consolidated Statement of Cash Flows	$177.0	$65.2	$78.9	$92.5

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	March 31, 2021	December 31, 2020
Millions
Fuel (a)	$20.4	$23.1
Materials and Supplies	53.6	51.1




Total Inventories – Net	$74.0	$74.2

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


Other Non-Current Assets	March 31, 2021	December 31, 2020
Millions
Contract Assets (a)	$24.8	$25.5

Operating Lease Right-of-use Assets	20.2	22.4
ALLETE Properties	18.2	18.2
Restricted Cash	10.9	20.1
Other Postretirement Benefit Plans	34.7	34.2
Other	82.5	86.4
Total Other Non-Current Assets	$191.3	$206.8

(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.

NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued)


Other Current Liabilities	March 31, 2021	December 31, 2020
Millions

PSAs	$12.5	$12.5



Fuel Adjustment Clause	1.8	3.7
Operating Lease Liabilities	5.7	5.9
Other	58.9	44.6
Total Other Current Liabilities	$78.9	$66.7


Other Non-Current Liabilities	March 31, 2021	December 31, 2020
Millions
Asset Retirement Obligation (a)	$170.8	$166.6
PSAs	48.9	52.1

Operating Lease Liabilities	14.5	16.5
Other	46.0	50.1
Total Other Non-Current Liabilities	$280.2	$285.3

(a)The asset retirement obligation is primarily related to our Regulated Operations and is funded through customer rates over the life of the related assets. Additionally, BNI Energy funds its obligation through its cost-plus coal supply agreements for which BNI Energy has recorded a receivable of $25.0 million in Other Non-Current Assets on the Consolidated Balance Sheet as of March 31, 2021 and December 31, 2020.


Other Income
Three Months Ended March 31,	2021	2020
Millions
Pension and Other Postretirement Benefit Plan Non-Service Credits (a)	$1.9	$2.6
Interest and Investment Income (Loss)	1.1	(2.6)
AFUDC - Equity	0.5	0.5
Gain on Land Sales	—	0.1
Other	(0.2)	0.4
Total Other Income	$3.3	$1.0

(a)These are components of net periodic pension and other postretirement benefit cost other than service cost. (See Note 9. Pension and Other Postretirement Benefit Plans.)

Supplemental Statement of Cash Flows Information.


Three Months Ended March 31,	2021	2020
Millions
Cash Paid for Interest – Net of Amounts Capitalized	$21.2	$18.3

Noncash Investing and Financing Activities

Increase in Accounts Payable for Capital Additions to Property, Plant and Equipment	$5.6	$4.7

Capitalized Asset Retirement Costs	$3.5	$1.6
AFUDC–Equity	$0.5	$0.5

Non-Controlling Interest in Subsidiaries. Non-controlling interest in subsidiaries on the Consolidated Balance Sheet and net loss attributable to non-controlling interest on the Consolidated Statement of Income represent the portion of equity ownership and earnings, respectively, of subsidiaries that are not attributable to equity holders of ALLETE. These amounts as of and during the quarter ended March 31, 2021, are primarily related to the tax equity financing structure for ALLETE Clean Energy’s 106 MW Glen Ullin, 80 MW South Peak and 303 MW Diamond Spring wind energy facilities as well as ALLETE’s equity investment in the 250 MW Nobles 2 wind energy facility.

NOTE 1. OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Continued)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

3 Months Ended

Mar. 31, 2021

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 2020 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 $9.6 million for the three months ended March 31, 2021 and 2020.

2020 Minnesota General Rate Case. In November 2019, Minnesota Power filed a retail rate increase request with the MPUC seeking an average increase of approximately 10.6 percent for retail customers. The rate filing sought a return on equity of 10.05 percent and a 53.81 percent equity ratio. On an annualized basis, the requested final rate increase would have generated approximately $66 million in additional revenue. In December 2019 orders, the MPUC accepted the filing as complete and authorized an annual interim rate increase of $36.1 million beginning January 1, 2020.

In April 2020, Minnesota Power filed a request with the MPUC that proposed a resolution of Minnesota Power’s 2020 general rate case. Key components of our proposal included removing the power marketing margin credit in base rates and reflecting actual power marketing margins in the fuel adjustment clause effective May 1, 2020; refunding to customers interim rates collected through April 2020; increasing customer rates 4.1 percent compared to the 5.8 percent increase reflected in interim rates; and a provision that Minnesota Power would not file another rate case until at least November 1, 2021, unless certain events occur. In a June 2020 order, the MPUC approved Minnesota Power’s petition and proposal to resolve and withdraw the general rate case. Effective May 1, 2020, customer rates were set at an increase of 4.1 percent with the removal of the power marketing margin credit from base rates. Actual power marketing margins will be reflected in the fuel adjustment clause. Reserves for interim rates of $11.7 million were recorded in the second quarter of 2020 and refunded in the third and fourth quarters of 2020.

Environmental Improvement Rider. Minnesota Power has an approved environmental improvement rider for investments and expenditures related to the implementation of the Boswell Unit 4 mercury emissions reduction plan completed in 2015. Updated customer billing rates for the environmental improvement rider were approved by the MPUC in a November 2018 order. On January 19, 2021, Minnesota Power filed a petition seeking MPUC approval to end the environmental improvement rider, which was approved in an order dated April 20, 2021.

Solar Cost Recovery Rider. In June 2020, Minnesota Power filed a petition seeking MPUC approval of a customer billing rate for solar costs related to investments and expenditures for meeting the state of Minnesota’s solar energy standard, which was approved by the MPUC in an order dated April 20, 2021.

Electric Vehicle Charging Infrastructure Petition. On April 8, 2021, Minnesota Power filed a petition seeking approval to install and own DC fast charger stations for electric vehicles across its service territory, implement accompanying rates for those stations, and track and recover investments and expenses for the project.

COVID-19 Related Deferred Accounting. In an order dated March 24, 2020, the PSCW authorized public utilities, including SWL&P, to defer expenditures incurred by the utility resulting from its compliance with state government or regulator orders during Wisconsin’s declared public health emergency for COVID-19. On April 20, 2020, Minnesota Power along with other regulated electric and natural gas service providers in Minnesota filed a joint petition to request MPUC authorization to track incremental costs and expenses incurred as a result of the COVID-19 pandemic, and to defer and record such costs as a regulatory asset, subject to recovery in a future proceeding. In an order dated May 22, 2020, the MPUC approved the joint petition requiring the joint petitioners to track cost and revenue impacts resulting from the COVID-19 pandemic with review for recovery in a future rate proceeding. As of March 31, 2021, Minnesota Power has not deferred any costs or lost revenue, and SWL&P has deferred an immaterial amount of costs.

NOTE 2. REGULATORY MATTERS (Continued)

Electric Rates (Continued)

Minnesota Power submitted a petition in November 2020 to the MPUC requesting authority to track and record as a regulatory asset lost large industrial customer revenue resulting from the idling of USS Corporation’s Keetac plant and Verso Corporation’s paper mill in Duluth, Minnesota. Keetac and Verso represent revenue of approximately $30 million annually, net of associated expense savings such as fuel costs. Minnesota Power proposed in this petition to defer any lost revenue related to the idling of the Keetac facility and the Verso paper mill to its next general rate case or other proceeding for review for recovery by the MPUC. At a hearing on April 1, 2021, the MPUC denied Minnesota Power’s request.

Fuel Adjustment Clause. In March 2020, Minnesota Power filed its fuel adjustment clause report covering the period July 2018 through December 2019. In a September 2020 order, the MPUC referred the review of Minnesota Power’s forced outage costs during the period of the report, which totaled approximately $8 million, to an administrative law judge for a contested case hearing to recommend to the MPUC if any of those costs should be returned to customers. A recommendation by the administrative law judge is expected in the third quarter of 2021. We cannot predict the outcome of this proceeding.

Conservation Improvement Program. On April 1, 2021, Minnesota Power submitted its 2020 consolidated filing detailing Minnesota Power’s CIP program results and requesting a CIP financial incentive of $2.4 million based upon MPUC procedures. CIP financial incentives are recognized in the period in which the MPUC approves the filing.

2021 Integrated Resource Plan. On February 1, 2021, Minnesota Power filed its latest IRP with the MPUC, which outlines its clean-energy transition plans through 2035. These plans include expanding its renewable energy supply, achieving coal-free operations at its facilities by 2035, and investing in a resilient and flexible transmission and distribution grid. As part of these plans, Minnesota Power anticipates adding approximately 400 MW of new wind and solar energy resources, retiring Boswell Unit 3 by 2030 and transforming Boswell Unit 4 to be coal-free by 2035. Minnesota Power’s plans recognize that advances in technology will play a significant role in completing its transition to carbon-free energy supply, reliably and affordably. A final decision on the IRP is expected in late 2021.

Nemadji Trail Energy Center. In 2017, Minnesota Power submitted a resource package to the MPUC which included requesting approval of a 250 MW natural gas capacity dedication and other affiliated-interest agreements for NTEC, a proposed 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 a January 2019 order, the MPUC approved Minnesota Power’s request for approval of the NTEC natural gas capacity dedication and other affiliated-interest agreements. In 2019, the Minnesota Court of Appeals reversed and remanded the MPUC’s decision to approve certain affiliated-interest agreements. The MPUC was ordered to determine whether NTEC may have the potential for significant environmental effects and, if so, to prepare an environmental assessment before reassessing the agreements. On January 22, 2020, Minnesota Power filed a petition for further review with the Minnesota Supreme Court requesting that it review and overturn the Minnesota Court of Appeals decision. On April 21, 2021, the Minnesota Supreme Court reversed the Minnesota Court of Appeal’s decision by ruling that the MPUC is not required to conduct review under the Minnesota Environmental Policy Act before approving affiliated-interest agreements that govern construction and operation of a Wisconsin power plant by a Minnesota utility, and remanded the case back to the Minnesota Court of Appeals for review of remaining issues on appeal. In January 2019, an application for a certificate of public convenience and necessity for NTEC was submitted to the PSCW, which was approved by the PSCW at a hearing in January 2020. Construction of NTEC is subject to obtaining additional permits from local, state and federal authorities. The total project cost is estimated to be approximately $700 million, of which ALLETE’s portion is expected to be approximately $350 million. ALLETE’s portion of NTEC project costs incurred through March 31, 2021, is approximately $15 million.

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 (Continued)


Regulatory Assets and Liabilities	March 31, 2021	December 31, 2020
Millions



Non-Current Regulatory Assets
Defined Benefit Pension and Other Postretirement Benefit Plans	$255.3	$259.7
Income Taxes	110.7	113.7
Cost Recovery Riders	57.5	54.0
Asset Retirement Obligations	31.5	31.6
Manufactured Gas Plant	5.8	8.8
Boswell Units 1 and 2 Net Plant and Equipment	3.6	5.0
PPACA Income Tax Deferral	4.5	4.5
Other	3.8	3.6
Total Non-Current Regulatory Assets	$472.7	$480.9


Current Regulatory Liabilities (a)
Fuel Adjustment Clause	$1.8	$3.7

Transmission Formula Rates Refund	2.4	2.9
Other	0.4	1.0
Total Current Regulatory Liabilities	4.6	7.6
Non-Current Regulatory Liabilities
Income Taxes	367.8	375.3
Wholesale and Retail Contra AFUDC	85.9	86.6
Plant Removal Obligations	43.0	41.2
Defined Benefit Pension and Other Postretirement Benefit Plans	3.4	4.4
North Dakota Investment Tax Credits	12.4	12.0

Conservation Improvement Program	1.7	1.5

Other	3.7	3.8
Total Non-Current Regulatory Liabilities	517.9	524.8
Total Regulatory Liabilities	$522.5	$532.4

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

Regulatory Assets and Liabilities [Table Text Block]


Regulatory Assets and Liabilities	March 31, 2021	December 31, 2020
Millions



Non-Current Regulatory Assets
Defined Benefit Pension and Other Postretirement Benefit Plans	$255.3	$259.7
Income Taxes	110.7	113.7
Cost Recovery Riders	57.5	54.0
Asset Retirement Obligations	31.5	31.6
Manufactured Gas Plant	5.8	8.8
Boswell Units 1 and 2 Net Plant and Equipment	3.6	5.0
PPACA Income Tax Deferral	4.5	4.5
Other	3.8	3.6
Total Non-Current Regulatory Assets	$472.7	$480.9


Current Regulatory Liabilities (a)
Fuel Adjustment Clause	$1.8	$3.7

Transmission Formula Rates Refund	2.4	2.9
Other	0.4	1.0
Total Current Regulatory Liabilities	4.6	7.6
Non-Current Regulatory Liabilities
Income Taxes	367.8	375.3
Wholesale and Retail Contra AFUDC	85.9	86.6
Plant Removal Obligations	43.0	41.2
Defined Benefit Pension and Other Postretirement Benefit Plans	3.4	4.4
North Dakota Investment Tax Credits	12.4	12.0

Conservation Improvement Program	1.7	1.5

Other	3.7	3.8
Total Non-Current Regulatory Liabilities	517.9	524.8
Total Regulatory Liabilities	$522.5	$532.4

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

Equity Investments

3 Months Ended

Mar. 31, 2021

Equity Method Investments and Joint Ventures [Abstract]

Equity Investments [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. We expect to make cash investments of approximately $2.0 million in 2021.


ALLETE’s Investment in ATC
Millions
Equity Investment Balance as of December 31, 2020			$149.0

Equity in ATC Earnings			5.3
Distributed ATC Earnings			(4.3)
Amortization of the Remeasurement of Deferred Income Taxes			0.3
Equity Investment Balance as of March 31, 2021			$150.3

ATC’s authorized return on equity is 10.02 percent, or 10.52 percent including an incentive adder for participation in a regional transmission organization, based on a May 2020 FERC order that granted rehearing of a 2019 FERC order.

NOTE 3. EQUITY INVESTMENTS (Continued)

Investment in Nobles 2. Our subsidiary, ALLETE South Wind, owns 49 percent of Nobles 2, the entity that owns and operates the 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.


ALLETE’s Investment in Nobles 2
Millions
Equity Investment Balance as of December 31, 2020			$152.2
Cash Investments			1.0
Equity in Nobles 2 Earnings (a)			(0.5)
Distributed Nobles 2 Earnings			(1.5)
Equity Investment Balance as of March 31, 2021			$151.2

(a)The Company also recorded net loss attributable to non-controlling interest of $1.4 million related to its investment in Nobles 2.

Fair Value

3 Months Ended

Mar. 31, 2021

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 6. Fair Value to the Consolidated Financial Statements in our 2020 Form 10-K.

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 March 31, 2021, and December 31, 2020. 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.

NOTE 4. FAIR VALUE (Continued)


	Fair Value as of March 31, 2021
Recurring Fair Value Measures	Level 1	Level 2	Level 3	Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities	$7.8	—	—	$7.8
Available-for-sale – Corporate and Governmental Debt Securities (b)	—	$9.3	—	9.3
Cash Equivalents	1.7	—	—	1.7
Total Fair Value of Assets	$9.5	$9.3	—	$18.8

Liabilities
Deferred Compensation (c)	—	$21.0	—	$21.0


Total Fair Value of Liabilities	—	$21.0	—	$21.0
Total Net Fair Value of Assets (Liabilities)	$9.5	$(11.7)	—	$(2.2)


	Fair Value as of December 31, 2020
Recurring Fair Value Measures	Level 1	Level 2	Level 3	Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities	$7.2	—	—	$7.2
Available-for-sale – Corporate and Governmental Debt Securities	—	$10.4	—	10.4
Cash Equivalents	5.5	—	—	5.5
Total Fair Value of Assets	$12.7	$10.4	—	$23.1

Liabilities
Deferred Compensation (c)	—	$21.0	—	$21.0

Total Fair Value of Liabilities	—	$21.0	—	$21.0
Total Net Fair Value of Assets (Liabilities)	$12.7	$(10.6)	—	$2.1

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

(b)As of March 31, 2021, the aggregate amount of available-for-sale corporate and governmental debt securities maturing in one year or less was $2.5 million, in one year to less than three years was $2.8 million, in three years to less than five years was $3.7 million and in five or more years was $0.3 million.

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

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 of the item listed in the following table was based on quoted market prices for the same or similar instruments (Level 2).


Financial Instruments	Carrying Amount	Fair Value
Millions
Short-Term and Long-Term Debt (a)
March 31, 2021	$1,960.1	$2,150.7
December 31, 2020	$1,806.4	$2,122.0

(a)Excludes unamortized debt issuance costs.

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 three months ended March 31, 2021, and the year ended December 31, 2020, there were no indicators of impairment for these non-financial assets.

We continue to monitor changes in the broader energy markets that could indicate impairment at ALLETE Clean Energy wind energy facilities upon contract expirations. A continued decline in energy prices could result in a future impairment.

- 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

3 Months Ended

Mar. 31, 2021

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 March 31, 2021, and December 31, 2020:


March 31, 2021	Principal	Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt	$298.8	$(0.3)	$298.5
Long-Term Debt	1,661.3	(8.9)	1,652.4
Total Debt	$1,960.1	$(9.2)	$1,950.9


December 31, 2020	Principal	Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt	$204.0	$(0.3)	$203.7
Long-Term Debt	1,602.4	(9.2)	1,593.2
Total Debt	$1,806.4	$(9.5)	$1,796.9

We had $24.3 million outstanding in standby letters of credit and $60.0 million outstanding draws under our lines of credit as of March 31, 2021 ($22.3 million in standby letters of credit and no outstanding draws as of December 31, 2020).

On March 25, 2021, ALLETE entered into a $150 million unsecured term loan agreement (Term Loan) and borrowed $100 million upon execution. The Term Loan provides for an additional draw of $50 million on or before May 29, 2021. The Term Loan is due March 24, 2022, and may be repaid at any time. Interest is payable monthly at a rate per annum equal to LIBOR plus 0.75 percent. Proceeds from the Term Loan were used for general corporate purposes.

On April 21, 2021, ALLETE agreed to sell $100 million of its First Mortgage Bonds (Bonds) to certain institutional buyers in the private placement market. The Bonds, which will be issued on or before September 1, 2021, will bear interest at 2.79 percent. The Bonds will mature in September 2031 and pay interest semi-annually in March and September of each year, commencing on March 1, 2022. 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.

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 March 31, 2021, 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 March 31, 2021, ALLETE was in compliance with its financial covenants.

Commitments, Guarantees and Contingencies	3 Months Ended
Commitments, Guarantees and Contingencies	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments, Guarantees and Contingencies [Text Block]	COMMITMENTS, GUARANTEES AND CONTINGENCIES Power Purchase and Sale 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 8. Commitments, Guarantees and Contingencies to the Consolidated Financial Statements in our 2020 Form 10-K, with additional disclosure provided in the following paragraphs. Square Butte PPA. As of March 31, 2021, Square Butte had total debt outstanding of $265.4 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 three months ended March 31, 2021, was $19.6 million ($20.1 million for the same period in 2020). 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 $1.5 million ($1.9 million for the same period in 2020). 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 2021 and in 2020. 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 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 retail and municipal utility customers through the fuel adjustment clause. 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 thermal 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 NOX technologies. Under currently applicable environmental regulations, these facilities are substantially compliant with emission requirements. NOTE 6. 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 NOX and SO2 allowances issued and pending issuance, we currently expect generation levels and emission rates will result in continued compliance with the CSAPR. The ongoing CSAPR “good neighbor” provision and interstate transport litigation is also not currently projected to affect Minnesota Power’s CSAPR compliance. The State of Minnesota has not been identified by the downwind litigant states as a culpable upwind source, and previous EPA air quality modeling has demonstrated that Minnesota is not a significant contributor to downwind air quality attainment challenges. Minnesota Power also does not currently anticipate being materially affected by the EPA’s recent rulemaking to address the remand of certain CSAPR aspects. Minnesota Power will continue to monitor ongoing CSAPR rulemakings and compliance implementation. 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. Minnesota Power actively monitors NAAQS developments and compliance costs for existing standards or proposed NAAQS revisions are not expected to be material. Minnesota is not among the states expected to be impacted by the EPA’s March 15, 2021 final rule to revise the 2016 CSAPR Update for the 2008 ozone NAAQS in response to the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) remand of the CSAPR Update Rule. 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 or other changes in 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. In 2019, the EPA finalized several separate rulemakings regarding regulating carbon emissions from electric utility generating units. These rulemakings included repealing the Clean Power Plan (CPP) and adopting the Affordable Clean Energy Rule under Section 111(d) of the Clean Air Act (CAA) to regulate CO2 emissions at existing coal-fired power plants. The CPP was first announced as a proposed rule under Section 111(d) of the CAA for existing power plants entitled “Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Generating Units”. The Affordable Clean Energy Rule established emissions guidelines for states to use when developing plans to limit CO2 coal-fired power plants. The EPA also published regulations for the state implementation of the Affordable Clean Energy Rule and other Section 111(d) rules. Affected facilities for Minnesota Power included Boswell Units 3 and 4, and Taconite Harbor Units 1 and 2, which are currently economically idled. On January 19, 2021, the D.C. Circuit issued an opinion vacating the Affordable Clean Energy Rule and remanded the Affordable Clean Energy Rule back to the EPA for further consideration, consistent with the D.C. Circuit’s finding that the EPA erred in interpreting the CAA, pending rehearing or appeal. On April 22, 2021, the Biden Administration announced a goal to reach 100 percent carbon pollution-free electricity by 2035 as part of the U.S.’s Nationally Determined Contributions pledge, which is part of an international effort to limit global warming. At this time, no specific regulatory pathway to achieve these reductions has been proposed. Minnesota Power will continue to monitor these developments. NOTE 6. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued) Environmental Matters (Continued) Minnesota had already initiated several measures consistent with those called for under the now repealed CPP and vacated 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. We are unable to predict the GHG emission compliance costs we might incur as a result of a replacement for the Affordable Clean Energy Rule or other future laws, regulations or administrative policies; however, the costs could be material. Minnesota Power would seek recovery of additional costs through a rate proceeding. Additionally on January 13, 2021, the EPA issued a rulemaking to apply CO2 emission New Source Performance Standards (NSPS) to new, modified and reconstructed fossil fuel-fired electric generating units under Section 111(b) of the CAA. Minnesota Power is monitoring the NSPS final rule and any further Section 111(b) developments including their potential impact to the Company. The Company’s proposed combined-cycle natural gas-fired generating facility, NTEC, is expected to meet these NSPS requirements. 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 reconsidered 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. On October 13, 2020, the EPA published a final ELG Rule allowing re-use of bottom ash transport water in FGD scrubber systems with limited discharges related to maintaining system water balance. The rule sets technology standards and numerical pollutant limits for discharges of bottom ash transport water and FGD wastewater. Compliance deadlines depend on subcategory, with compliance generally required as soon as possible, beginning after October 13, 2021, but no later than December 31, 2023, or December 31, 2028, in some specific cases. The rule also establishes new subcategories for retiring high-flow and low-utilization units, and establishes a voluntary incentives program for FGD wastewater. The 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. With Boswell’s planned conversion to dry FGD handling and storage, ongoing FGD water generation will be reduced, and the majority of FGD waters will be legacy waters to be dewatered from existing impoundments. Re-use and onsite consumption for the majority of FGD waters is planned at Boswell. Under the new ELG rule, most bottom ash transport water discharge to surface waters must cease no later than December 31, 2025, except for small discharges needed to retain water balance. The majority of bottom ash transport water will either need to be re-used in a closed-loop process or routed to a FGD scrubber. At Boswell, the bottom ash handling systems are planned to be converted to a dry process, which will eliminate bottom ash transport water. The EPA’s additional reconsideration of legacy wastewater discharge requirements have the potential to reduce timelines 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 estimate that the planned dry conversion of bottom ash handling and storage at Boswell in response to the CCR revisions requiring closure of clay-lined impoundments, as well as other water re-use practices, will reduce or eliminate the need for additional significant compliance costs for ELG bottom ash water and FGD requirements. Compliance costs we might incur related to other ELG waste streams (e.g. legacy leachate) or other potential future water discharge regulations cannot be estimated; however, the costs could be material, including costs associated with wastewater treatment and re-use. Minnesota Power would seek recovery of additional costs through a rate proceeding. NOTE 6. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued) Environmental Matters (Continued) Permitted Water Discharges – Sulfate. In 2017, the MPCA released a draft water quality standard in an attempt to update Minnesota’s existing 10 mg/L sulfate limit for waters used for the production of wild rice with the proposed rulemaking heard before an Administrative Law Judge (ALJ). In 2018, the ALJ rejected significant portions of the proposed rulemaking and the MPCA subsequently withdrew the rulemaking. The remaining 10 mg/L standard remains in place, but the MPCA is currently prohibited under state law from listing wild rice waters as impaired or requiring sulfate reduction technology. In April 2021, the MPCA’s proposed list of impaired waters was partially rejected by EPA due to the absence of wild rice waters listed for sulfate impairment. The EPA subsequently proposed a list of 30 wild rice waters for public comment in a separate listing process on April 29, 2021, with public comment through May 31, 2021. A final impaired waters listing is expected to follow the public comment period, which could subsequently be used to set sulfate limits in discharge permits for power generation facilities and municipal and industrial customers, including paper and pulp facilities, and mining operations. At this time we are unable to determine the specific impacts these developments may have on Minnesota Power operations, if any. 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 produces the majority of its coal ash at Boswell, with small amounts of ash generated at Hibbard Renewable Energy Center. Ash storage and disposal methods include storing ash in clay-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. 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. In March 2018, the EPA published the first phase of the proposed rule revisions in the Federal Register. In 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 2018, a U.S. District Court for the District of Columbia decision vacated specific provisions of the CCR rule. The court decision resulted in a change to the status of three existing clay-lined impoundments at Boswell that must now be considered unlined. The EPA proposed additional rule revisions in 2019 to address outstanding issues from litigation and closure timelines for unlined impoundments, respectively. The first of these rules, CCR Rule Part A, was finalized in September 2020. The Part A Rule revision requires unlined impoundments to cease disposal of waste as soon as technically feasible but no later than April 11, 2021, which tolls forward if the EPA does not make a determination on a variance application by that date. Minnesota Power sought EPA approval to extend the closure date for the two active Boswell impoundments in November 2020, and continues to operate the impoundments pending a final determination by the EPA. Additionally, the EPA released a proposed Part B rulemaking in February 2020 that addressed options for beneficial reuse of CCR materials, alternative liner demonstrations, and other CCR regulatory revisions. Portions of the Part B Rule addressing alternative liner equivalency standards were finalized in November 2020. According to the EPA’s current regulatory agenda, the remainder of the proposed Part B Rule is expected to be finalized in mid-2021. Expected compliance costs at Boswell due to the court decision and subsequent rule revisions are reflected in our estimate of compliance costs for the CCR rule noted previously. Minnesota Power would seek recovery of additional costs through a rate proceeding. NOTE 6. COMMITMENTS, GUARANTEES AND CONTINGENCIES (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, and formerly operated by SWL&P. SWL&P has been working with the Wisconsin Department of Natural Resources (WDNR) in determining the extent and location of contamination at the site and surrounding properties. In January 2021, SWL&P submitted a final remedial actions options report to the WDNR with remedial site design expected to be completed in 2021. As of March 31, 2021, we have recorded a liability of approximately $7 million for remediation costs at this site (approximately $7 million as of December 31, 2020); however, SWL&P continues to work with the WDNR on the extent of contamination which may result in additional remediation costs being identified. SWL&P has also recorded 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. Letters of Credit and Surety Bonds. We have multiple credit facility agreements in place that provide the ability to issue standby letters of credit to satisfy our contractual security requirements across our businesses. As of March 31, 2021, we had $119.0 million of outstanding letters of credit issued, including those issued under our revolving credit facility. Regulated Operations. As of March 31, 2021, we had $30.8 million outstanding in standby letters of credit at our Regulated Operations which are pledged as security for MISO and state agency agreements as well as energy facilities under development. ALLETE Clean Energy. ALLETE Clean Energy’s wind energy facilities have PSAs in place for their entire output and expire in various years between 2022 and 2039. As of March 31, 2021, ALLETE Clean Energy has $74.4 million outstanding in standby letters of credit, the majority of which are pledged as security under these PSAs and PSAs for wind energy facilities under development. ALLETE Clean Energy does not believe it is likely that any of these outstanding letters of credit will be drawn upon. Corporate and Other. Investment in Nobles 2. Construction of the Nobles 2 wind energy facility requires standby letters of credit as security for certain contractual obligations. As of March 31, 2021, ALLETE South Wind has $13.8 million outstanding in standby letters of credit, related to its portion of the security requirements relative to its ownership in Nobles 2. BNI Energy. As of March 31, 2021, BNI Energy had surety bonds outstanding of $71.2 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 $70.7 million. BNI Energy does not believe it is likely that any of these outstanding surety bonds will be drawn upon. ALLETE Properties. As of March 31, 2021, ALLETE Properties had surety bonds outstanding and letters of credit to governmental entities totaling $2.0 million primarily related to development and maintenance obligations for various projects. The estimated cost of the remaining development work is $1.0 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 March 31, 2021, we owned 48 percent of the assessable land in the Town Center District (48 percent as of December 31, 2020). As of March 31, 2021, ownership levels, our annual assessments related to capital improvement and special assessment bonds for the ALLETE Properties project within the district is approximately $1.8 million. As we sell property at this project, 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. NOTE 6. COMMITMENTS, GUARANTEES AND CONTINGENCIES (Continued) Other Matters (Continued) 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.

Earnings Per Share and Common Stock

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Earnings Per Share and Common Stock [Text Block]

EARNINGS PER SHARE AND COMMON STOCK

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.


		2021			2020
Reconciliation of Basic and Diluted		Dilutive			Dilutive
Earnings Per Share	Basic	Securities	Diluted	Basic	Securities	Diluted
Millions Except Per Share Amounts




Three Months Ended March 31,
Net Income Attributable to ALLETE	$51.8		$51.8	$66.3		$66.3
Average Common Shares	52.1	0.1	52.2	51.7	0.1	51.8
Earnings Per Share	$0.99		$0.99	$1.28		$1.28

Income Tax Expense

3 Months Ended

Mar. 31, 2021

Income Tax Disclosure [Abstract]

Income Tax Expense [Text Block]

INCOME TAX EXPENSE


	Three Months Ended
	March 31,
		2021	2020
Millions
Current Income Tax Expense (a)
Federal		—	—
State		—	—
Total Current Income Tax Expense		—	—
Deferred Income Tax Expense (Benefit)
Federal (b)		$(14.1)	$(17.6)
State		3.9	4.0
Investment Tax Credit Amortization		(0.2)	(0.2)
Total Deferred Income Tax Benefit		$(10.4)	$(13.8)
Total Income Tax Benefit		$(10.4)	$(13.8)

(a)For each of the three months ended March 31, 2021 and 2020, the federal and state current tax expense was minimal due to NOLs which resulted from the bonus depreciation provisions of certain tax legislation. Federal and state NOLs are being carried forward to offset current and future taxable income.

(b)For each of the three months ended March 31, 2021 and 2020, the federal income tax benefit is primarily due to production tax credits.

NOTE 8. INCOME TAX EXPENSE (Continued)

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.


	Three Months Ended
Reconciliation of Taxes from Federal Statutory	March 31,
Rate to Total Income Tax Expense		2021		2020
Millions
Income Before Income Taxes		$33.0		$50.7


Statutory Federal Income Tax Rate		21	%	21	%
Income Taxes Computed at Statutory Federal Rate		$6.9		$10.6
Increase (Decrease) in Income Tax Due to:
State Income Taxes – Net of Federal Income Tax Benefit		3.1		3.2


Production Tax Credits		(18.6)		(23.8)
Regulatory Differences – Excess Deferred Tax		(3.2)		(4.4)

Non-Controlling Interest in Subsidiaries		1.8		0.4
Share-Based Compensation		0.5		(0.1)
Other		(0.9)		0.3
Total Income Tax Benefit		$(10.4)		$(13.8)

For the three months ended March 31, 2021, the effective tax rate was a benefit of 31.5 percent (benefit of 27.2 percent for the three months ended March 31, 2020). The effective tax rate for 2020 and 2021 was primarily impacted by production tax credits.

Uncertain Tax Positions. As of March 31, 2021, we had gross unrecognized tax benefits of $1.5 million ($1.4 million as of December 31, 2020). 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 2017, or state examination for years before 2016.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Pension and Other Postretirement Benefit Plans

3 Months Ended

Mar. 31, 2021

Retirement Benefits [Abstract]

Pension and Other Postretirement Benefit Plans [Text Block]

PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS


	Pension		Other Postretirement
Components of Net Periodic Benefit Cost (Credit)	2021	2020	2021	2020
Millions










Three Months Ended March 31,
Service Cost	$2.7	$2.6	$0.9	$0.8
Non-Service Cost Components (a)
Interest Cost	6.1	7.0	1.1	1.3
Expected Return on Plan Assets	(10.8)	(10.7)	(2.4)	(2.5)
Amortization of Prior Service Credits	—	—	(1.9)	(2.0)
Amortization of Net Loss	4.7	3.2	0.7	0.3

Net Periodic Benefit Cost (Credit)	$2.7	$2.1	$(1.6)	$(2.1)

(a)These components of net periodic benefit cost (credit) are included in the line item “Other” under Other Income (Expense) on the Consolidated Statement of Income.

NOTE 9. PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Continued)

Employer Contributions. For the three months ended March 31, 2021, we contributed $10.3 million in cash to the defined benefit pension plans ($10.7 million for the three months ended March 31, 2020); we do not expect to make additional contributions to our defined benefit pension plans in 2021. For the three months ended March 31, 2021 and 2020, we made no contributions to our other postretirement benefit plans; we do not expect to make any contributions to our other postretirement benefit plans in 2021.

- Definition

The entire disclosure for retirement benefits.

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+ Details

Business Segments

3 Months Ended

Mar. 31, 2021

Segment Reporting [Abstract]

Business Segments [Text Block]

BUSINESS SEGMENTS

We present two reportable segments: Regulated Operations and ALLETE Clean Energy. 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. 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.


	Three Months Ended
	March 31,
		2021	2020
Millions
Operating Revenue
Regulated Operations
Residential		$45.6	$40.9
Commercial		39.7	37.3
Municipal		12.6	10.3
Industrial		129.0	118.8
Other Power Suppliers		38.4	38.3

Other		27.7	19.7
Total Regulated Operations		293.0	265.3

ALLETE Clean Energy
Long-term PSA		18.1	17.3
Other		2.8	2.8
Total ALLETE Clean Energy		20.9	20.1







Corporate and Other
Long-term Contract		21.7	22.4
Other		3.6	3.8
Total Corporate and Other		25.3	26.2

Total Operating Revenue		$339.2	$311.6
Net Income (Loss) Attributable to ALLETE
Regulated Operations		$45.0	$57.5

ALLETE Clean Energy		7.4	11.7



Corporate and Other		(0.6)	(2.9)
Total Net Income Attributable to ALLETE		$51.8	$66.3

NOTE 10. BUSINESS SEGMENTS (Continued)


	March 31, 2021	December 31, 2020
Millions
Assets
Regulated Operations	$4,184.1	$4,196.8

ALLETE Clean Energy	1,596.6	1,483.3

Corporate and Other	493.8	404.5
Total Assets	$6,274.5	$6,084.6

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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-Name Accounting Standards Codification
-Topic 280
-URI http://asc.fasb.org/topic&trid=2134510

+ Details

Operations and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
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.
Regulatory Assets and Liabilities [Policy Text Block]	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 ATC under the equity method of accounting.We account for our investment in Nobles 2 under the equity method of accounting.
Fair Value Measurement [Policy Text Block]	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. 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.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.
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 two reportable segments: Regulated Operations and ALLETE Clean Energy. 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)

3 Months Ended

Mar. 31, 2021

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	March 31, 2021	December 31, 2020	March 31, 2020	December 31, 2019
Millions
Cash and Cash Equivalents	$159.0	$44.3	$67.0	$69.3
Restricted Cash included in Prepayments and Other	7.1	0.8	6.1	2.8
Restricted Cash included in Other Non-Current Assets	10.9	20.1	5.8	20.4
Cash, Cash Equivalents and Restricted Cash on the Consolidated Statement of Cash Flows	$177.0	$65.2	$78.9	$92.5

Inventories – Net [Table Text Block]


Inventories – Net	March 31, 2021	December 31, 2020
Millions
Fuel (a)	$20.4	$23.1
Materials and Supplies	53.6	51.1




Total Inventories – Net	$74.0	$74.2

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

Other Non-Current Assets [Table Text Block]


Other Non-Current Assets	March 31, 2021	December 31, 2020
Millions
Contract Assets (a)	$24.8	$25.5

Operating Lease Right-of-use Assets	20.2	22.4
ALLETE Properties	18.2	18.2
Restricted Cash	10.9	20.1
Other Postretirement Benefit Plans	34.7	34.2
Other	82.5	86.4
Total Other Non-Current Assets	$191.3	$206.8

Other Current Liabilities [Table Text Block]


Other Current Liabilities	March 31, 2021	December 31, 2020
Millions

PSAs	$12.5	$12.5



Fuel Adjustment Clause	1.8	3.7
Operating Lease Liabilities	5.7	5.9
Other	58.9	44.6
Total Other Current Liabilities	$78.9	$66.7

Other Non-Current Liabilities [Table Text Block]


Other Non-Current Liabilities	March 31, 2021	December 31, 2020
Millions
Asset Retirement Obligation (a)	$170.8	$166.6
PSAs	48.9	52.1

Operating Lease Liabilities	14.5	16.5
Other	46.0	50.1
Total Other Non-Current Liabilities	$280.2	$285.3

Other Income [Table Text Block]


Other Income
Three Months Ended March 31,	2021	2020
Millions
Pension and Other Postretirement Benefit Plan Non-Service Credits (a)	$1.9	$2.6
Interest and Investment Income (Loss)	1.1	(2.6)
AFUDC - Equity	0.5	0.5
Gain on Land Sales	—	0.1
Other	(0.2)	0.4
Total Other Income	$3.3	$1.0

(a)These are components of net periodic pension and other postretirement benefit cost other than service cost. (See Note 9. Pension and Other Postretirement Benefit Plans.)

Supplemental Statement of Cash Flows Information [Table Text Block]

Supplemental Statement of Cash Flows Information.


Three Months Ended March 31,	2021	2020
Millions
Cash Paid for Interest – Net of Amounts Capitalized	$21.2	$18.3

Noncash Investing and Financing Activities

Increase in Accounts Payable for Capital Additions to Property, Plant and Equipment	$5.6	$4.7

Capitalized Asset Retirement Costs	$3.5	$1.6
AFUDC–Equity	$0.5	$0.5

Regulatory Matters (Tables)

3 Months Ended

Mar. 31, 2021

Regulated Operations [Abstract]

Regulatory Assets and Liabilities [Table Text Block]


Regulatory Assets and Liabilities	March 31, 2021	December 31, 2020
Millions



Non-Current Regulatory Assets
Defined Benefit Pension and Other Postretirement Benefit Plans	$255.3	$259.7
Income Taxes	110.7	113.7
Cost Recovery Riders	57.5	54.0
Asset Retirement Obligations	31.5	31.6
Manufactured Gas Plant	5.8	8.8
Boswell Units 1 and 2 Net Plant and Equipment	3.6	5.0
PPACA Income Tax Deferral	4.5	4.5
Other	3.8	3.6
Total Non-Current Regulatory Assets	$472.7	$480.9


Current Regulatory Liabilities (a)
Fuel Adjustment Clause	$1.8	$3.7

Transmission Formula Rates Refund	2.4	2.9
Other	0.4	1.0
Total Current Regulatory Liabilities	4.6	7.6
Non-Current Regulatory Liabilities
Income Taxes	367.8	375.3
Wholesale and Retail Contra AFUDC	85.9	86.6
Plant Removal Obligations	43.0	41.2
Defined Benefit Pension and Other Postretirement Benefit Plans	3.4	4.4
North Dakota Investment Tax Credits	12.4	12.0

Conservation Improvement Program	1.7	1.5

Other	3.7	3.8
Total Non-Current Regulatory Liabilities	517.9	524.8
Total Regulatory Liabilities	$522.5	$532.4

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

Equity Investments (Tables)

3 Months Ended

Mar. 31, 2021

ATC [Member]

Investment in ATC [Line Items]

Equity Method Investments (Table Text Block)


ALLETE’s Investment in ATC
Millions
Equity Investment Balance as of December 31, 2020			$149.0

Equity in ATC Earnings			5.3
Distributed ATC Earnings			(4.3)
Amortization of the Remeasurement of Deferred Income Taxes			0.3
Equity Investment Balance as of March 31, 2021			$150.3

Nobles 2 [Member]

Investment in ATC [Line Items]

Equity Method Investments (Table Text Block)


ALLETE’s Investment in Nobles 2
Millions
Equity Investment Balance as of December 31, 2020			$152.2
Cash Investments			1.0
Equity in Nobles 2 Earnings (a)			(0.5)
Distributed Nobles 2 Earnings			(1.5)
Equity Investment Balance as of March 31, 2021			$151.2

(a)The Company also recorded net loss attributable to non-controlling interest of $1.4 million related to its investment in Nobles 2.

Fair Value (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Recurring Fair Value Measures [Table Text Block]


	Fair Value as of March 31, 2021
Recurring Fair Value Measures	Level 1	Level 2	Level 3	Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities	$7.8	—	—	$7.8
Available-for-sale – Corporate and Governmental Debt Securities (b)	—	$9.3	—	9.3
Cash Equivalents	1.7	—	—	1.7
Total Fair Value of Assets	$9.5	$9.3	—	$18.8

Liabilities
Deferred Compensation (c)	—	$21.0	—	$21.0


Total Fair Value of Liabilities	—	$21.0	—	$21.0
Total Net Fair Value of Assets (Liabilities)	$9.5	$(11.7)	—	$(2.2)


	Fair Value as of December 31, 2020
Recurring Fair Value Measures	Level 1	Level 2	Level 3	Total
Millions
Assets
Investments (a)
Available-for-sale – Equity Securities	$7.2	—	—	$7.2
Available-for-sale – Corporate and Governmental Debt Securities	—	$10.4	—	10.4
Cash Equivalents	5.5	—	—	5.5
Total Fair Value of Assets	$12.7	$10.4	—	$23.1

Liabilities
Deferred Compensation (c)	—	$21.0	—	$21.0

Total Fair Value of Liabilities	—	$21.0	—	$21.0
Total Net Fair Value of Assets (Liabilities)	$12.7	$(10.6)	—	$2.1

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

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

Fair Value, by Balance Sheet Grouping [Table Text Block]


Financial Instruments	Carrying Amount	Fair Value
Millions
Short-Term and Long-Term Debt (a)
March 31, 2021	$1,960.1	$2,150.7
December 31, 2020	$1,806.4	$2,122.0

(a)Excludes unamortized debt issuance costs.

Short-Term and Long-Term Debt (Tables)

3 Months Ended

Mar. 31, 2021

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 March 31, 2021, and December 31, 2020:


March 31, 2021	Principal	Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt	$298.8	$(0.3)	$298.5
Long-Term Debt	1,661.3	(8.9)	1,652.4
Total Debt	$1,960.1	$(9.2)	$1,950.9


December 31, 2020	Principal	Unamortized Debt Issuance Costs	Total
Millions
Short-Term Debt	$204.0	$(0.3)	$203.7
Long-Term Debt	1,602.4	(9.2)	1,593.2
Total Debt	$1,806.4	$(9.5)	$1,796.9

Earnings Per Share and Common Stock (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Reconciliation of Basic and Diluted Earnings Per Share [Table Text Block]


		2021			2020
Reconciliation of Basic and Diluted		Dilutive			Dilutive
Earnings Per Share	Basic	Securities	Diluted	Basic	Securities	Diluted
Millions Except Per Share Amounts




Three Months Ended March 31,
Net Income Attributable to ALLETE	$51.8		$51.8	$66.3		$66.3
Average Common Shares	52.1	0.1	52.2	51.7	0.1	51.8
Earnings Per Share	$0.99		$0.99	$1.28		$1.28

Income Tax Expense (Tables)

3 Months Ended

Mar. 31, 2021

Income Tax Disclosure [Abstract]

Income Tax Expense [Table Text Block]


	Three Months Ended
	March 31,
		2021	2020
Millions
Current Income Tax Expense (a)
Federal		—	—
State		—	—
Total Current Income Tax Expense		—	—
Deferred Income Tax Expense (Benefit)
Federal (b)		$(14.1)	$(17.6)
State		3.9	4.0
Investment Tax Credit Amortization		(0.2)	(0.2)
Total Deferred Income Tax Benefit		$(10.4)	$(13.8)
Total Income Tax Benefit		$(10.4)	$(13.8)

(b)For each of the three months ended March 31, 2021 and 2020, the federal income tax benefit is primarily due to production tax credits.

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


	Three Months Ended
Reconciliation of Taxes from Federal Statutory	March 31,
Rate to Total Income Tax Expense		2021		2020
Millions
Income Before Income Taxes		$33.0		$50.7


Statutory Federal Income Tax Rate		21	%	21	%
Income Taxes Computed at Statutory Federal Rate		$6.9		$10.6
Increase (Decrease) in Income Tax Due to:
State Income Taxes – Net of Federal Income Tax Benefit		3.1		3.2


Production Tax Credits		(18.6)		(23.8)
Regulatory Differences – Excess Deferred Tax		(3.2)		(4.4)

Non-Controlling Interest in Subsidiaries		1.8		0.4
Share-Based Compensation		0.5		(0.1)
Other		(0.9)		0.3
Total Income Tax Benefit		$(10.4)		$(13.8)

Pension and Other Postretirement Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2021

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Expense (Income) [Table Text Block]


	Pension		Other Postretirement
Components of Net Periodic Benefit Cost (Credit)	2021	2020	2021	2020
Millions










Three Months Ended March 31,
Service Cost	$2.7	$2.6	$0.9	$0.8
Non-Service Cost Components (a)
Interest Cost	6.1	7.0	1.1	1.3
Expected Return on Plan Assets	(10.8)	(10.7)	(2.4)	(2.5)
Amortization of Prior Service Credits	—	—	(1.9)	(2.0)
Amortization of Net Loss	4.7	3.2	0.7	0.3

Net Periodic Benefit Cost (Credit)	$2.7	$2.1	$(1.6)	$(2.1)

(a)These components of net periodic benefit cost (credit) are included in the line item “Other” under Other Income (Expense) on the Consolidated Statement of Income.

Business Segments (Tables)

3 Months Ended

Mar. 31, 2021

Segment Reporting [Abstract]

Business Segments [Table Text Block]


	Three Months Ended
	March 31,
		2021	2020
Millions
Operating Revenue
Regulated Operations
Residential		$45.6	$40.9
Commercial		39.7	37.3
Municipal		12.6	10.3
Industrial		129.0	118.8
Other Power Suppliers		38.4	38.3

Other		27.7	19.7
Total Regulated Operations		293.0	265.3

ALLETE Clean Energy
Long-term PSA		18.1	17.3
Other		2.8	2.8
Total ALLETE Clean Energy		20.9	20.1







Corporate and Other
Long-term Contract		21.7	22.4
Other		3.6	3.8
Total Corporate and Other		25.3	26.2

Total Operating Revenue		$339.2	$311.6
Net Income (Loss) Attributable to ALLETE
Regulated Operations		$45.0	$57.5

ALLETE Clean Energy		7.4	11.7



Corporate and Other		(0.6)	(2.9)
Total Net Income Attributable to ALLETE		$51.8	$66.3

NOTE 10. BUSINESS SEGMENTS (Continued)


	March 31, 2021	December 31, 2020
Millions
Assets
Regulated Operations	$4,184.1	$4,196.8

ALLETE Clean Energy	1,596.6	1,483.3

Corporate and Other	493.8	404.5
Total Assets	$6,274.5	$6,084.6

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

Mar. 31, 2021

Dec. 31, 2020

Mar. 31, 2020

Dec. 31, 2019

Cash, Cash Equivalents and Restricted Cash [Abstract]

Cash and Cash Equivalents

$ 159.0

$ 44.3

$ 67.0

$ 69.3

Restricted Cash included in Prepayments and Other

7.1

0.8

6.1

2.8

Restricted Cash, Non-Current

10.9

20.1

5.8

20.4

Total Cash, Cash Equivalents and Restricted Cash

177.0

65.2

78.9

92.5

Inventories – Net [Abstract]

Fuel

^[1]

20.4

23.1

Materials and Supplies

53.6

51.1

Total Inventories – Net

74.0

74.2

Other Non-Current Assets [Abstract]

Contract Assets

^[2]

24.8

25.5

Operating Lease, Right-of-Use Asset

20.2

22.4

ALLETE Properties

18.2

Restricted Cash, Non-Current

10.9

20.1

$ 5.8

$ 20.4

Other Postretirement Benefit Plans

34.7

34.2

Other

82.5

86.4

Total Other Non-Current Assets

191.3

206.8

Other Current Liabilites [Abstract]

PSAs

12.5

Public Utilities, Fuel Adjustment Clause

1.8

3.7

Operating Lease Liabilities

5.7

5.9

Other

58.9

44.6

Total Other Current Liabilities

78.9

66.7

Other Non-Current Liabilities [Abstract]

Asset Retirement Obligation (a)

^[3]

170.8

166.6

PSAs

48.9

52.1

Operating Lease Liabilities

14.5

16.5

Other

46.0

50.1

Total Other Non-Current Liabilities

280.2

285.3

BNI Energy

Business Segments [Line Items]

Other Receivables

$ 25.0

[1]	Fuel consists primarily of coal inventory at Minnesota Power.
[2]	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.
[3]	The asset retirement obligation is primarily related to our Regulated Operations and is funded through customer rates over the life of the related assets. Additionally, BNI Energy funds its obligation through its cost-plus coal supply agreements for which BNI Energy has recorded a receivable of $25.0 million in Other Non-Current Assets on the Consolidated Balance Sheet as of March 31, 2021 and December 31, 2020.

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

3 Months Ended

Mar. 31, 2021

Mar. 31, 2020

Other Income (Expense) - Other [Line Items]

Total Other Income

$ 3.3

$ 1.0

Pension and Other Postretirement Benefit Plans Non-Service Credit [Member]

Other Income (Expense) - Other [Line Items]

Total Other Income

^[1]

1.9

2.6

Interest and Investment Income (Loss) [Member]

Other Income (Expense) - Other [Line Items]

Total Other Income

1.1

(2.6)

AFUDC - Equity [Member]

Other Income (Expense) - Other [Line Items]

Total Other Income

0.5

Gain on Land Sales [Member]

Other Income (Expense) - Other [Line Items]

Total Other Income

0.0

0.1

Other [Member]

Other Income (Expense) - Other [Line Items]

Total Other Income

$ (0.2)

$ 0.4

[1]	These are components of net periodic pension and other postretirement benefit cost other than service cost. (See Note 9. Pension and Other Postretirement Benefit Plans.)

Operations and Significant Accounting Policies - Non-Controlling Interest (Details)	3 Months Ended
	Mar. 31, 2021 MW
South Peak [Member]
Non-Controlling Interest Details [Line Items]
Generating Capacity Subject to Tax Equity Financing	80
Glen Ullin Energy Center [Member]
Non-Controlling Interest Details [Line Items]
Generating Capacity Subject to Tax Equity Financing	106
Nobles 2 [Member]
Non-Controlling Interest Details [Line Items]
Generating Capacity Subject to Tax Equity Financing	250
Diamond Spring
Non-Controlling Interest Details [Line Items]
Generating Capacity Subject to Tax Equity Financing	303

Regulatory Matters - Electric Rates (Details) - MPUC [Member] - Minnesota Power [Member] - USD ($) $ in Millions				3 Months Ended		4 Months Ended	18 Months Ended
	Apr. 01, 2021	May 01, 2020	Nov. 01, 2019	Mar. 31, 2021	Mar. 31, 2020	Apr. 30, 2020	Dec. 31, 2019	Dec. 31, 2020
CIP Consolidated Filing [Member] \| Subsequent Event [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs	$ 2.4
Fuel Adjustment Clause Filing [Member]
Regulatory Matters [Line Items]
Forced Outage Costs							$ 8.0
COVID-19 Related Deferred Accounting [Member]
Regulatory Matters [Line Items]
Estimated Annual Reduction to Revenue Due to Idled Customers Keetac and Verso				$ 30.0
Electric Rates [Member] \| Minnesota Cost Recovery Riders [Member] \| Retail Customers [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs				$ 9.6	$ 9.6
Electric Rates [Member] \| 2020 Minnesota General Rate Case [Member] \| Retail Customers [Member]
Regulatory Matters [Line Items]
Annual Additional Revenue Generated from Requested Final Rate Increase			$ 66.0
Requested Rate Increase Percent			10.60%
Interim Rate Increase						$ 36.1
Requested Return on Equity			10.05%
Requested Equity Capital Structure			53.81%
Ongoing Customer Rate Increase		4.10%
Public Utilities, Interim Rate Increase (Decrease), Percentage						5.80%
Public Utilities Reserve for Interim Rates								$ 11.7

Regulatory Matters - Nemadji Trail Energy Center (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) MW
Nemadji Trail Energy Center [Member] \| Maximum [Member]
Regulatory Matters [Line Items]
Estimated Capital Expenditures, Including Past Expenditures \| $	$ 700
ALLETE, Inc. [Member] \| Nemadji Trail Energy Center [Member]
Regulatory Matters [Line Items]
Estimated Capital Expenditures, Including Past Expenditures \| $	350
ALLETE, Inc. [Member] \| Nemadji Trail Energy Center [Member] \| Maximum [Member]
Regulatory Matters [Line Items]
Total Project Costs Incurred to Date \| $	$ 15
MPUC [Member] \| Resource Package [Member] \| 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) \| MW	525
MPUC [Member] \| Resource Package [Member] \| 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) \| MW	550
MPUC [Member] \| Resource Package [Member] \| Minnesota Power [Member] \| Natural Gas PPA [Member]
Regulatory Matters [Line Items]
Output Being Purchased (MW) \| MW	250
MPUC [Member] \| Resource Package [Member] \| Minnesota Power [Member] \| Natural Gas-fired [Member] \| Natural Gas PPA [Member]
Regulatory Matters [Line Items]
Expected Output Entitlement (Percent)	50.00%

Regulatory Matters - Integrated Resource Plan (Details) - Renewable Generation - 2021 Integrated Resource Plan - MPUC [Member]	Mar. 31, 2021 MW
Regulated Operations [Abstract]
Anticipated Additional Generating Capacity (MW)	400
Regulatory Matters [Line Items]
Anticipated Additional Generating Capacity (MW)	400

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

3 Months Ended

Mar. 31, 2021

Dec. 31, 2020

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

$ 472.7

$ 480.9

Current Regulatory Liabilities

^[1]

4.6

7.6

Non-Current Regulatory Liabilities

517.9

524.8

Total Regulatory Liabilities

522.5

532.4

Regulatory Clause Revenues, under-recovered

Regulatory Assets and Liabilities [Line Items]

Current Regulatory Liabilities

^[1]

1.8

3.7

Transmission Formula Rates [Member]

Regulatory Assets and Liabilities [Line Items]

Current Regulatory Liabilities

^[1]

2.4

2.9

Income Taxes [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

367.8

375.3

Wholesale and Retail Contra AFUDC [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

85.9

86.6

Plant Removal Obligations [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

43.0

41.2

Pension and Other Postretirement Plan Costs [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

3.4

4.4

North Dakota Investment Tax Credits [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

12.4

12.0

Conservation Improvement Program [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Liabilities

1.7

1.5

Other

Regulatory Assets and Liabilities [Line Items]

Current Regulatory Liabilities

^[1]

0.4

1.0

Non-Current Regulatory Liabilities

3.7

3.8

Pension and Other Postretirement Plan Costs [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

255.3

259.7

Income Taxes [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

110.7

113.7

Cost Recovery Riders [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

57.5

54.0

Asset Retirement Obligations [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

31.5

31.6

Manufactured Gas Plant [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

5.8

8.8

Boswell Units 1 and 2 Net Plant and Equipment [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

3.6

5.0

PPACA Income Tax Deferral [Member]

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

4.5

Other

Regulatory Assets and Liabilities [Line Items]

Non-Current Regulatory Assets

$ 3.8

$ 3.6

[1]	Current regulatory liabilities are presented within Other Current Liabilities on the Consolidated Balance Sheet

Equity Investments - Investment in ATC (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
ALLETE's Investment in ATC [Roll Forward]
Equity Investment Balance as of December 31, 2020	$ 301.2
Cash Investments	1.0	$ 27.8
Equity in ATC Earnings	4.8	$ 5.2
Equity Investment Balance as of March 31, 2021	$ 301.5
ATC [Member]
Investment in ATC [Line Items]
Ownership Percentage	8.00%
ALLETE's Investment in ATC [Roll Forward]
Equity Investment Balance as of December 31, 2020	$ 149.0
Equity in ATC Earnings	5.3
Distributed ATC Earnings	(4.3)
Amortization of the Remeasurement of Deferred Income Taxes	0.3
Equity Investment Balance as of March 31, 2021	$ 150.3
Authorized Return on Equity	10.02%
Authorized Return on Equity, Including Incentive Adder	10.52%
Equity Method Investment, Expected Additional Investment Next Fiscal Year	$ 2.0

Equity Investments - Investment in Nobles 2 (Details)
$ in Millions

3 Months Ended

Mar. 31, 2021

USD ($)

Mar. 31, 2020

USD ($)

Dec. 31, 2020

USD ($)

Investment in Nobles 2 [Line Items]

Equity Investment Balance

$ 301.5

$ 301.2

Cash Investments

1.0

$ 27.8

Equity Earnings

4.8

5.2

Net Loss Attributable to Non-Controlling Interest

$ (8.4)

$ (1.8)

Nobles 2 [Member]

Investment in Nobles 2 [Line Items]

Ownership Percentage

49.00%

Equity Investment Balance

$ 151.2

152.2

Cash Investments

1.0

Distributed ATC Earnings

(1.5)

Equity Earnings

^[1]

(0.5)

Net Loss Attributable to Non-Controlling Interest

$ 1.4

ATC [Member]

Investment in Nobles 2 [Line Items]

Ownership Percentage

8.00%

Equity Investment Balance

$ 150.3

$ 149.0

Distributed ATC Earnings

(4.3)

Equity Earnings

$ 5.3

Wind Turbine Generators [Member] | Tenaska [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

[1]	The Company also recorded net loss attributable to non-controlling interest of $1.4 million related to its investment in Nobles 2.

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

Mar. 31, 2021

Dec. 31, 2020

Investments [Abstract]

Available-for-sale Securities, Debt Maturities, within One Year, Fair Value

$ 2.5

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

2.8

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

3.7

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

0.3

Recurring Fair Value Measures [Member]

Investments [Abstract]

Available-for-sale – Equity Securities

^[1]

7.8

$ 7.2

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

^[1]

9.3

^[2]

10.4

Cash Equivalents

^[1]

1.7

5.5

Total Fair Value of Assets

18.8

23.1

Liabilities [Abstract]

Deferred Compensation

^[3]

21.0

Total Fair Value of Liabilities

21.0

Total Net Fair Value of Assets (Liabilities)

(2.2)

2.1

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

Investments [Abstract]

Available-for-sale – Equity Securities

^[1]

7.8

7.2

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

^[1]

0.0

^[2]

0.0

Cash Equivalents

^[1]

1.7

5.5

Total Fair Value of Assets

9.5

12.7

Liabilities [Abstract]

Deferred Compensation

^[3]

0.0

Total Fair Value of Liabilities

0.0

Total Net Fair Value of Assets (Liabilities)

9.5

12.7

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]

9.3

^[2]

10.4

Cash Equivalents

^[1]

0.0

Total Fair Value of Assets

9.3

10.4

Liabilities [Abstract]

Deferred Compensation

^[3]

21.0

Total Fair Value of Liabilities

21.0

Total Net Fair Value of Assets (Liabilities)

(11.7)

(10.6)

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

Total Fair Value of Liabilities

0.0

Total Net Fair Value of Assets (Liabilities)

$ 0.0

[1]	Included in Other Non-Current Assets on the Consolidated Balance Sheet.
[2]	As of March 31, 2021, the aggregate amount of available-for-sale corporate and governmental debt securities maturing in one year or less was $2.5 million, in one year to less than three years was $2.8 million, in three years to less than five years was $3.7 million and in five or more years was $0.3 million.
[3]	Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.

Fair Value - Fair Value of Financial Instruments and Assets Measured on a Nonrecurring Basis (Details) - USD ($)
$ in Millions

Mar. 31, 2021

Dec. 31, 2020

Fair Value of Financial Instruments [Line Items]

Short-Term and Long-Term Debt - Carrying Amount

^[1]

$ 1,960.1

$ 1,806.4

Level 2 [Member]

Fair Value of Financial Instruments [Line Items]

Short-Term and Long-Term Debt - Fair Value

^[1]

$ 2,150.7

$ 2,122.0

[1]	Excludes unamortized debt issuance costs.

Short-Term and Long-Term Debt (Details) - USD ($) $ in Millions		3 Months Ended
	Apr. 21, 2021	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Short-Term Debt - Principal		$ 298.8	$ 204.0
Short-Term Debt - Unamortized Debt Issuance Costs		(0.3)	(0.3)
Short-Term Debt - Total		298.5	203.7
Long-Term Debt - Principal		1,661.3	1,602.4
Long-Term Debt - Unamortized Debt Issuance Costs		(8.9)	(9.2)
Long-Term Debt - Total		1,652.4	1,593.2
Total Debt - Principal		1,960.1	1,806.4
Total Debt - Unamortized Debt Issuance Costs		(9.2)	(9.5)
Total Debt - Total		1,950.9	1,796.9
Unsecured Term Loan Due in 2022
Debt Instrument [Line Items]
Unsecured Term Loan, Amount		150.0
Proceeds from Short-term Debt		100.0
Debt Instrument, Unused Borrowing Capacity, Amount		$ 50.0
Variable Rate Basis		LIBOR
Basis Spread on Variable Rate		0.75%
Line of Credit [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		$ 24.3	22.3
Line of Credit, Current		$ 60.0	$ 0.0
Subsequent Event [Member] \| ALLETE Bonds 2.79% Due September 2031
Debt Instrument [Line Items]
Proceeds from Issuance of First Mortgage Bond	$ 100.0
Interest Rate	2.79%

Short-Term and Long-Term Debt - Financial Covenants (Details)	Mar. 31, 2021
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

Commitments, Guarantees and Contingencies - Power Purchase Agreements (Details) - Square Butte PPA [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Square Butte [Member]
Power Purchase Agreements [Line Items]
PPA Counterparty Total Debt Outstanding	$ 265.4
Square Butte [Member] \| Minnesota Power [Member]
Power Purchase Agreements [Line Items]
Cost of Power Purchased	19.6	$ 20.1
Pro Rata Share of PPA Counterparty Interest Expense	$ 1.5	$ 1.9
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 - Environmental Matters (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
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	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Regulated Operations [Member] \| Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Letters of Credit Outstanding, Amount	$ 30.8
ALLETE Clean Energy [Member] \| Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Letters of Credit Outstanding, Amount	74.4
BNI Energy Reclamation Liability [Member]
Guarantor Obligations [Line Items]
Estimated Obligation	70.7
BNI Energy Reclamation Liability [Member] \| Surety Bonds [Member]
Guarantor Obligations [Line Items]
Collateral	71.2
ALLETE Properties Development and Maintenance Obligations [Member]
Guarantor Obligations [Line Items]
Estimated Obligation	1.0
ALLETE Properties Development and Maintenance Obligations [Member] \| Surety Bonds [Member]
Guarantor Obligations [Line Items]
Collateral	$ 2.0
Town Center District Capital Improvement Bonds [Member]
Guarantor Obligations [Line Items]
Ownership Percentage of Benefited Property	48.00%	48.00%
Annual Assessment	$ 1.8
ALLETE South Wind [Member] \| Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Letters of Credit Outstanding, Amount	13.8
ALLETE, Inc. [Member] \| Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Letters of Credit Outstanding, Amount	$ 119.0

Earnings Per Share and Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share - Basic [Abstract]
Net Income Attributable ALLETE	$ 51.8	$ 66.3
Average Common Shares	52.1	51.7
Earnings Per Share	$ 0.99	$ 1.28
Earnings Per Share - Diluted [Abstract]
Net Income Attributable to ALLETE	$ 51.8	$ 66.3
Average Common Shares	52.2	51.8
Earnings Per Share	$ 0.99	$ 1.28
Dilutive Securities (Shares)	0.1	0.1

- Definition

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

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+ Details

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

3 Months Ended

Mar. 31, 2021

Mar. 31, 2020

Dec. 31, 2020

Current Income Tax Expense (Benefit) [Abstract]

Federal

^[1]

$ 0.0

State

^[1]

0.0

Total Current Income Tax Expense

0.0

Deferred Income Tax Expense (Benefit) [Abstract]

Federal

^[2]

(14.1)

(17.6)

State

3.9

4.0

Investment Tax Credit Amortization

(0.2)

Total Deferred Income Tax Expense (Benefit)

(10.4)

(13.8)

Total Income Tax Expense (Benefit)

(10.4)

(13.8)

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

Income Before Income Taxes

$ 33.0

$ 50.7

Statutory Federal Income Tax Rate

21.00%

Income Taxes Computed at Statutory Federal Rate

$ 6.9

$ 10.6

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

State Income Taxes – Net of Federal Income Tax Benefit

3.1

3.2

Production Tax Credits

(18.6)

(23.8)

Regulatory Differences – Excess Deferred Tax

(3.2)

(4.4)

Non-Controlling Interest in Subsidiaries

1.8

0.4

Share-Based Compensation

0.5

(0.1)

Other

(0.9)

0.3

Total Income Tax Expense (Benefit)

$ (10.4)

$ (13.8)

Effective Tax Rate

(31.50%)

(27.20%)

Uncertain Tax Positions [Abstract]

Gross Unrecognized Tax Benefits

$ 1.5

$ 1.4

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

$ 0.6

[1]	For each of the three months ended March 31, 2021 and 2020, the federal and state current tax expense was minimal due to NOLs which resulted from the bonus depreciation provisions of certain tax legislation. Federal and state NOLs are being carried forward to offset current and future taxable income.
[2]	For each of the three months ended March 31, 2021 and 2020, the federal income tax benefit is primarily due to production tax credits.

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

3 Months Ended

Mar. 31, 2021

Mar. 31, 2020

Pension [Member]

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

Service Cost

$ 2.7

$ 2.6

Interest Cost

^[1]

6.1

7.0

Expected Return on Plan Assets

^[1]

(10.8)

(10.7)

Amortization of Prior Service Credits

^[1]

0.0

Amortization of Net Loss

^[1]

4.7

3.2

Net Periodic Benefit Cost (Credit)

2.7

2.1

Employer Contributions to Defined Benefit Plans

10.3

10.7

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

0.0

Business Segments (Details) $ in Millions	3 Months Ended
Business Segments (Details) $ in Millions	Mar. 31, 2021 USD ($) a Segments	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Business Segments [Line Items]
Number of Reportable Segments \| Segments	2
Operating Revenue	$ 339.2	$ 311.6
Net Income (Loss) Attributable to ALLETE	51.8	66.3
Assets	$ 6,274.5		$ 6,084.6
Regulated Operations [Member]
Business Segments [Line Items]
Number of Operating Segments \| Segments	3
Operating Revenue	$ 293.0	265.3
Net Income (Loss) Attributable to ALLETE	45.0	57.5
Assets	4,184.1		4,196.8
Regulated Operations [Member] \| Residential [Member]
Business Segments [Line Items]
Operating Revenue	45.6	40.9
Regulated Operations [Member] \| Commercial [Member]
Business Segments [Line Items]
Operating Revenue	39.7	37.3
Regulated Operations [Member] \| Municipal [Member]
Business Segments [Line Items]
Operating Revenue	12.6	10.3
Regulated Operations [Member] \| Industrial [Member]
Business Segments [Line Items]
Operating Revenue	129.0	118.8
Regulated Operations [Member] \| Other Power Suppliers [Member]
Business Segments [Line Items]
Operating Revenue	38.4	38.3
Regulated Operations [Member] \| Other [Member]
Business Segments [Line Items]
Operating Revenue	27.7	19.7
ALLETE Clean Energy [Member]
Business Segments [Line Items]
Operating Revenue	20.9	20.1
Net Income (Loss) Attributable to ALLETE	7.4	11.7
Assets	1,596.6		1,483.3
ALLETE Clean Energy [Member] \| Long-term PSA [Member]
Business Segments [Line Items]
Operating Revenue	18.1	17.3
ALLETE Clean Energy [Member] \| Other [Member]
Business Segments [Line Items]
Operating Revenue, Other Than Customer Revenue	$ 2.8	2.8
Corporate and Other [Member]
Business Segments [Line Items]
Number of Operating Segments \| Segments	2
Land in Minnesota (Acres) \| a	4,000
Operating Revenue	$ 25.3	26.2
Net Income (Loss) Attributable to ALLETE	(0.6)	(2.9)
Assets	493.8		$ 404.5
Corporate and Other [Member] \| Long-term Contract [Member]
Business Segments [Line Items]
Operating Revenue	21.7	22.4
Corporate and Other [Member] \| Other [Member]
Business Segments [Line Items]
Operating Revenue	$ 3.6	$ 3.8