Schedule I-Condensed Financial Information of Registrant - Notes to Condensed Financial Statements (Details)			12 Months Ended
	Nov. 15, 2023 USD ($)	Nov. 10, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Nov. 06, 2023 USD ($)	May 31, 2023 USD ($)	May 01, 2023 USD ($)
Condensed Financial Statements, Captions [Line Items]
Short-term borrowings			$ 95,000,000	$ 38,500,000
Long-term debt			2,298,223,000	2,365,667,000
Repayments of long-term debt			792,998,000	65,764,000	$ 24,758,000
Repayment of short-term borrowings			460,901,000	0	100,000,000
Long-term debt, maturities year two			$ 347,700,000
MDU Resources Group, Inc. | Revolving Credit Facility
Condensed Financial Statements, Captions [Line Items]
Ratio of total debt to total capitalization			0.65
Long-term debt							$ 200,000,000
MDU Resources Group, Inc. | Term Loan Agreement
Condensed Financial Statements, Captions [Line Items]
Ratio of total debt to total capitalization			65
Long-term debt							375,000,000
Repayments of long-term debt	$ 185,000,000
MDU Resources Group, Inc. | Revolving Credit Facility
Condensed Financial Statements, Captions [Line Items]
Short-term borrowings			$ 0				$ 150,000,000
Ratio of total debt to total capitalization							0.65
Term Loan Agreement | MDU Resources Group, Inc.
Condensed Financial Statements, Captions [Line Items]
Short-term borrowings						$ 310,000,000		$ 75,000,000
Repayment of short-term borrowings		$ 293,200,000
MDU Resources Group, Inc.
Condensed Financial Statements, Captions [Line Items]
Repayments of long-term debt			385,000,000	0	0
Repayment of short-term borrowings			242,401,000	0	0
Long-term debt, maturities year two			190,000,000
Cash dividends paid to parent company by consolidated subsidiaries			$ 165,500,000	$ 242,100,000	$ 188,100,000