Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating activities:
Net cash provided by continuing operations	$ 411,813	$ 305,333	$ 321,615
Net cash provided by discontinued operations	90,505	27,294	188,449
Net cash provided by operating activities	502,318	332,627	510,064
Investing activities:
Investments	(5,155)	(2,423)	(2,571)
Net cash used in continuing operations	(523,827)	(465,129)	(456,929)
Financing activities:
Issuance of short-term borrowings	0	810,000	11,500
Repayment of short-term borrowings	(95,000)	(433,901)	0
Issuance of long-term debt	308,600	594,700	214,969
Repayment of long-term debt	(182,135)	(568,883)	(38,764)
Debt issuance costs	(2,456)	(2,521)	(1,129)
Costs of issuance of common stock	(50)	0	(150)
Dividends paid	(102,939)	(161,316)	(176,915)
Repurchase of common stock	0	(4,811)	(7,399)
Tax withholding on stock-based compensation	(2,623)	(3,040)	(4,904)
Net cash (used in) provided by continuing operations	(76,603)	230,228	(2,792)
Net cash provided by (used in) discontinued operations	116,899	(25,606)	157,965
Net cash provided by financing activities	40,296	204,622	155,173
(Decrease) increase in cash, cash equivalents and restricted cash	(10,071)	(3,542)	26,356
Cash, cash equivalents and restricted cash - beginning of year	60,473
Cash, cash equivalents and restricted cash - end of year	66,904	60,473
MDU Resources Group, Inc.
Operating activities:
Net cash provided by continuing operations	482,195	282,132	253,663
Net cash provided by discontinued operations	(40,007)	(58,591)	(11,464)
Net cash provided by operating activities	442,188	223,541	242,199
Investing activities:
Investments	2,253	7,422	(885)
Repayment (issuance) of notes receivable	58,000	(58,000)	0
Net cash used in continuing operations	(150,747)	(526,578)	(45,885)
Financing activities:
Issuance of short-term borrowings	0	535,000	0
Repayment of short-term borrowings	0	(242,401)	0
Issuance of long-term debt	0	443,000	0
Repayment of long-term debt	(58,000)	(385,000)	0
Debt issuance costs	(401)	(952)	0
Costs of issuance of common stock	(50)	0	(149)
Dividends paid	(102,939)	(161,316)	(176,915)
Repurchase of common stock	0	(2,270)	(3,525)
Tax withholding on stock-based compensation	(1,729)	(1,471)	(2,398)
Net cash (used in) provided by continuing operations	(163,119)	184,590	(182,987)
Net cash provided by (used in) discontinued operations	(132,000)	132,000	0
Net cash provided by financing activities	(295,119)	316,590	(182,987)
(Decrease) increase in cash, cash equivalents and restricted cash	(3,678)	13,553	13,327
Cash, cash equivalents and restricted cash - beginning of year	33,039	19,486	6,159
Cash, cash equivalents and restricted cash - end of year	29,361	33,039	19,486
MDU Resources Group, Inc. | Subsidiaries
Investing activities:
Investments	$ (211,000)	$ (476,000)	$ (45,000)