v3.19.3
Document and Entity Information Document
9 Months Ended
Sep. 30, 2019
shares
Document and Entity Information [Line Items]  
Document Type 10-Q
Document Quarterly Report true
Document Period End Date Sep. 30, 2019
Document Transition Report false
Entity File Number 1-3548
Entity Registrant Name ALLETE, Inc.
State of Incorporation MN
Entity Tax Identification Number 41-0418150
Entity Address, Address Line One 30 West Superior Street
Entity Address, City or Town Duluth
Entity Address, State or Province MN
Entity Address, Postal Zip Code 55802-2093
City Area Code 218
Local Phone Number 279-5000
Title of 12(b) Security Common Stock, without par value
Trading Symbol ALE
Name of Exchange NYSE
Entity Current Reporting Status Yes
Entity Interactive Data Current Yes
Entity Filer Category Large Accelerated Filer
Entity Shell Company false
Entity Common Stock, Shares Outstanding 51,668,047
Entity Central Index Key 0000066756
Current Fiscal Year End Date --12-31
Document Fiscal Year Focus 2019
Document Fiscal Period Focus Q3
Amendment Flag false
Entity Small Business false
Entity Emerging Growth Company false