v3.25.2
Document and Entity Information Document
Jul. 30, 2025
Cover [Abstract]  
Document Type 8-K
Entity Registrant Name NorthWestern Energy Group, Inc.
Entity File Number 000-56598
Entity Incorporation, State or Country Code DE
Entity Tax Identification Number 93-2020320
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
Entity Emerging Growth Company false
Title of 12(b) Security Common stock
Entity Central Index Key 0001993004
Amendment Flag false
Trading Symbol NWE
Security Exchange Name NASDAQ
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Document Period End Date Jul. 30, 2025