Schedule I-Condensed Financial Information of Registrant - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net cash provided by continuing operations	$ 492,757	$ 307,653	$ 298,947
Net cash (used in) provided by discontinued operations	(160,130)	202,411	196,830
Net cash provided by operating activities	332,627	510,064	495,777
Investing activities:
Investments	16,302	(4,138)	(3,136)
Net cash used in continuing operations	(485,780)	(483,003)	(487,611)
Financing activities:
Issuance of short-term borrowings	810,000	38,500	50,000
Repayment of short-term borrowings	(460,901)	0	(100,000)
Issuance of long-term debt	726,700	373,046	272,043
Repayment of long-term debt	(792,998)	(65,764)	(24,758)
Debt issuance costs	(2,521)	(1,129)	(918)
Proceeds from issuance of common stock	0	(150)	88,767
Dividends paid	(161,316)	(176,915)	(171,354)
Repurchase of common stock	(4,811)	(7,399)	(6,701)
Tax withholding on stock-based compensation	(3,040)	(4,904)	(4,126)
Net cash provided by continuing operations	111,113	155,285	102,953
Increase (decrease) in cash, cash equivalents and restricted cash	(3,542)	26,356	(5,386)
Cash, cash equivalents and restricted cash - beginning of year	70,428
Cash, cash equivalents and restricted cash - end of year	76,975	70,428
MDU Resources Group, Inc.
Operating activities:
Net cash provided by continuing operations	271,337	251,204	187,297
Net cash (used in) provided by discontinued operations	(47,796)	(9,005)	0
Net cash provided by operating activities	223,541	242,199	187,297
Investing activities:
Investments	7,422	(885)	(391)
Issuance of notes receivable	(58,000)	0	0
Net cash used in continuing operations	(526,578)	(45,885)	(102,391)
Financing activities:
Issuance of short-term borrowings	535,000	0	0
Repayment of short-term borrowings	(242,401)	0	0
Issuance of long-term debt	575,000	0	0
Repayment of long-term debt	(385,000)	0	0
Debt issuance costs	(952)	0	0
Proceeds from issuance of common stock	0	(149)	88,767
Dividends paid	(161,316)	(176,915)	(171,354)
Repurchase of common stock	(2,270)	(3,525)	(2,992)
Tax withholding on stock-based compensation	(1,471)	(2,398)	(1,949)
Net cash provided by continuing operations	316,590	(182,987)	(87,528)
Increase (decrease) in cash, cash equivalents and restricted cash	13,553	13,327	(2,622)
Cash, cash equivalents and restricted cash - beginning of year	19,486	6,159	8,781
Cash, cash equivalents and restricted cash - end of year	33,039	19,486	6,159
MDU Resources Group, Inc. | Subsidiaries
Investing activities:
Investments	$ (476,000)	$ (45,000)	$ (102,000)