Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 54,161	$ 59,547
Receivables, net	946,741	873,986
Inventories	335,609	291,167
Current regulatory assets	118,691	68,527
Prepayments and other current assets	95,741	44,120
Total current assets	1,550,943	1,337,347
Noncurrent assets:
Property, plant and equipment	8,972,849	8,300,770
Less accumulated depreciation, depletion and amortization	3,216,461	3,133,831
Net property, plant and equipment	5,756,388	5,166,939
Goodwill	765,386	714,963
Other intangible assets, net	22,578	25,496
Regulatory assets	357,851	379,381
Investments	175,476	165,022
Operating lease right-of-use assets	124,138	120,113
Other	157,675	144,111
Total noncurrent assets	7,359,492	6,716,025
Total assets	8,910,435	8,053,372
Current liabilities:
Short-term borrowings	0	50,000
Long-term debt due within one year	148,053	1,555
Accounts payable	478,933	426,264
Taxes payable	80,372	88,844
Dividends payable	44,229	42,611
Accrued compensation	81,904	90,629
Operating lease liabilities due within one year	35,368	33,655
Regulatory liabilities due within one year	16,303	31,450
Other accrued liabilities	207,078	198,514
Total current liabilities	1,092,240	963,522
Noncurrent liabilities:
Long-term debt	2,593,847	2,211,575
Deferred income taxes	591,962	516,098
Asset retirement obligations	458,061	440,356
Regulatory liabilities	428,790	428,075
Operating lease liabilities	89,253	86,868
Other	273,408	327,773
Total noncurrent liabilities	4,435,321	4,010,745
Commitments and contingencies
Stockholders' equity:
Common stock	203,889	201,061
Other paid-in capital	1,461,205	1,371,385
Retained earnings	1,762,410	1,558,363
Accumulated other comprehensive loss	(41,004)	(48,078)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)
Total stockholders' equity	3,382,874	3,079,105
Total liabilities and stockholders' equity	$ 8,910,435	$ 8,053,372
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par 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	$ 8,781
Receivables, net	6,120	4,865
Prepayments and other current assets	2,528	1,612
Total current assets	64,503	65,797
Noncurrent assets:
Investments	55,686	52,000
Operating lease right-of-use assets	114	56
Other	26,558	28,866
Total noncurrent assets	3,458,259	3,160,569
Total assets	3,522,762	3,226,366
Current liabilities:
Accounts payable	2,546	2,135
Taxes payable	1,672	4,056
Dividends payable	44,229	42,611
Accrued compensation	4,098	7,825
Operating lease liabilities due within one year	52	40
Other accrued liabilities	7,309	6,881
Total current liabilities	66,039	68,960
Noncurrent liabilities:
Operating lease liabilities	62	16
Other	73,787	78,285
Total noncurrent liabilities	73,849	78,301
Commitments and contingencies
Stockholders' equity:
Common stock	203,889	201,061
Other paid-in capital	1,461,205	1,371,385
Retained earnings	1,762,410	1,558,363
Accumulated other comprehensive loss	(41,004)	(48,078)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)
Total stockholders' equity	3,382,874	3,079,105
Total liabilities and stockholders' equity	$ 3,522,762	$ 3,226,366
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par 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