Condensed Statements of Cash Flows (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 495,777	$ 768,374	$ 542,280
Capital expenditures	(659,425)	(558,007)	(576,065)
Net proceeds from sale or disposition of property and other	15,238	35,557	29,812
Investments	(3,973)	(1,814)	(2,011)
Net cash used in investing activities	(885,878)	(630,243)	(603,861)
Issuance of long-term debt	554,027	117,450	603,969
Repayment of long-term debt	(24,979)	(148,634)	(468,917)
Proceeds from issuance of common stock	88,767	3,385	106,848
Dividends paid	(171,354)	(166,405)	(160,256)
Repurchase of common stock	(6,701)	0	0
Tax withholding on stock-based compensation	(4,127)	(362)	(3,015)
Net cash used in financing activities	384,715	(145,043)	74,092
Cash and cash equivalents - beginning of year	59,547	66,459	53,948
Cash and cash equivalents - end of year	54,161	59,547	66,459
MDU Resources Group, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	187,297	226,642	168,520
Investments in and advances to subsidiaries	(102,000)	(67,000)	(120,000)
Advances from subsidiaries	0	0	17,000
Investments	(391)	(4)	(236)
Net cash used in investing activities	(102,391)	(67,004)	(103,236)
Proceeds from issuance of common stock	88,767	3,385	106,848
Dividends paid	(171,354)	(166,405)	(160,256)
Repurchase of common stock	(2,992)	0	0
Tax withholding on stock-based compensation	(1,949)	(163)	(1,821)
Net cash used in financing activities	(87,528)	(163,183)	(55,229)
Increase (decrease) in cash and cash equivalents	(2,622)	(3,545)	10,055
Cash and cash equivalents - beginning of year	8,781	12,326	2,271
Cash and cash equivalents - end of year	$ 6,159	$ 8,781	$ 12,326