Condensed Balance Sheets (Details 2) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 54,161,000	$ 59,547,000	$ 66,459,000	$ 53,948,000
Receivables, net	946,741,000	873,986,000
Prepayments and other current assets	95,741,000	44,120,000
Assets, Current	1,550,943,000	1,337,347,000
Noncurrent Assets
Investments	175,476,000	165,022,000
Operating lease right-of-use assets	124,138,000	120,113,000
Other	157,675,000	144,111,000
Total noncurrent assets	7,359,492,000	6,716,025,000
Total assets	8,910,435,000	8,053,372,000	7,683,059,000
Current liabilities:
Accounts payable	478,933,000	426,264,000
Taxes payable	80,372,000	88,844,000
Dividends payable	44,229,000	42,611,000
Accrued compensation	81,904,000	90,629,000
Operating lease liabilities due within one year	35,368,000	33,655,000
Other accrued liabilities	207,078,000	198,514,000
Total current liabilities	1,092,240,000	963,522,000
Noncurrent liabilities:
Operating lease liabilities	89,253,000	86,868,000
Other	273,408,000	327,773,000
Total noncurrent liabilities	4,435,321,000	4,010,745,000
Commitments and contingencies
Commitments and Contingencies
Stockholders' equity:
Common stock	203,889,000	201,061,000
Other paid-in capital	1,461,205,000	1,371,385,000
Retained earnings	1,762,410,000	1,558,363,000
Accumulated other comprehensive loss	(41,004,000)	(48,078,000)
Treasury stock at cost - 538,921 shares	(3,626,000)	(3,626,000)
Stockholders' Equity Attributable to Parent	3,382,874,000	3,079,105,000
Total liabilities and stockholders' equity	$ 8,910,435,000	$ 8,053,372,000
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares, Issued	203,889,661	201,061,198
Treasury Stock, Common, Shares	538,921	538,921
MDU Resources Group, Inc. [Member]
Current assets:
Cash and cash equivalents	$ 6,159,000	$ 8,781,000	$ 12,326,000	$ 2,271,000
Receivables, net	6,120,000	4,865,000
Accounts receivable from subsidiaries	49,696,000	50,539,000
Prepayments and other current assets	2,528,000	1,612,000
Assets, Current	64,503,000	65,797,000
Noncurrent Assets
Investments	55,686,000	52,000,000
Investment in subsidiaries	3,368,537,000	3,069,956,000
Deferred income taxes	7,364,000	9,691,000
Operating lease right-of-use assets	114,000	56,000
Other	26,558,000	28,866,000
Total noncurrent assets	3,458,259,000	3,160,569,000
Total assets	3,522,762,000	3,226,366,000
Current liabilities:
Accounts payable	2,546,000	2,135,000
Accounts payable to subsidiaries	6,133,000	5,412,000
Taxes payable	1,672,000	4,056,000
Dividends payable	44,229,000	42,611,000
Accrued compensation	4,098,000	7,825,000
Operating lease liabilities due within one year	52,000	40,000
Other accrued liabilities	7,309,000	6,881,000
Total current liabilities	66,039,000	68,960,000
Noncurrent liabilities:
Operating lease liabilities	62,000	16,000
Other	73,787,000	78,285,000
Total noncurrent liabilities	73,849,000	78,301,000
Commitments and contingencies
Commitments and Contingencies
Stockholders' equity:
Common stock	203,889,000	201,061,000
Other paid-in capital	1,461,205,000	1,371,385,000
Retained earnings	1,762,410,000	1,558,363,000
Accumulated other comprehensive loss	(41,004,000)	(48,078,000)
Treasury stock at cost - 538,921 shares	(3,626,000)	(3,626,000)
Stockholders' Equity Attributable to Parent	3,382,874,000	3,079,105,000
Total liabilities and stockholders' equity	$ 3,522,762,000	$ 3,226,366,000
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00
Common Stock, Shares, Issued	203,889,661	201,061,198
Treasury Stock, Common, Shares	538,921	538,921