v3.23.3

Document and Entity Information Document	Oct. 26, 2023
Document Information [Line Items]
Document Type	8-K
Entity Registrant Name	NorthWestern Corporation
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	0000073088
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	Oct. 26, 2023
Northwestern Energy Corporation
Document Information [Line Items]
Document Type	8-K
Entity File Number	1-10499
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-0172280
Amendment Flag	false
Written Communications	false
Soliciting Material	false
Pre-commencement Tender Offer	false
Pre-commencement Issuer Tender Offer	false
Northwestern Energy Group Inc.
Document Information [Line Items]
Entity Registrant Name	NorthWestern Energy Group, Inc.
Entity Central Index Key	0001993004

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Area code of city

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.

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The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

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Address Line 1 such as Attn, Building Name, Street Name

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Name of the City or Town

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Code for the postal or zip code

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Name of the state or province.

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A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

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Two-character EDGAR code representing the state or country of incorporation.

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The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Local phone number for entity.

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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Title of a 12(b) registered security.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Name of the Exchange on which a security is registered.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Trading symbol of an instrument as listed on an exchange.

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Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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NORTHWESTERN CORP 8-K