Document and Entity Information
Document and Entity Information Document | Oct. 27, 2020 | Sep. 24, 2020 |
Cover [Abstract] | ||
Document Type | 8-K | |
Document Period End Date | Oct. 27, 2020 | |
Entity Registrant Name | NorthWestern Corp | |
Entity Central Index Key | 0000073088 | |
Amendment Flag | false | |
Entity Incorporation, State or Country Code | DE | |
Entity File Number | 1-10499 | |
Entity Tax Identification Number | 46-0172280 | |
Entity Address, Address Line One | 3010 W. 69th Street | |
Entity Address, City or Town | Sioux Falls | |
Entity Address, State or Province | SD | |
Entity Address, Postal Zip Code | 57108 | |
City Area Code | 605 | |
Local Phone Number | 978-2900 | |
Written Communications | false | |
Soliciting Material | false | |
Pre-commencement Tender Offer | false | |
Pre-commencement Issuer Tender Offer | false | |
Title of 12(b) Security | Common stock | |
Trading Symbol | NWE | |
Security Exchange Name | NASDAQ | |
Entity Emerging Growth Company | false |