XML 10 R1.htm IDEA: XBRL DOCUMENT v3.21.1
Cover
May 11, 2021
May 12, 2020
Cover [Abstract]    
Document Type 8-K  
Document Period End Date May 11, 2021  
Entity Registrant Name ALLETE, Inc  
Entity Incorporation, State or Country Code MN  
Entity File Number 1-3548  
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  
Written Communications false  
Soliciting Material false  
Pre-commencement Tender Offer false  
Pre-commencement Issuer Tender Offer false  
Title of 12(b) Security Common Stock, without par value  
Trading Symbol ALE  
Security Exchange Name NYSE  
Entity Emerging Growth Company false  
Entity Central Index Key   0000066756
Amendment Flag   false