Schedule I-Condensed Financial Information of Registrant - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 76,975	$ 70,428
Receivables, net	942,782	1,064,340
Prepayments and other current assets	84,082	55,123
Total current assets	1,363,723	2,011,748
Noncurrent assets
Investments	124,235	128,827
Operating lease right-of-use assets	74,363	73,502
Other	211,865	161,901
Total noncurrent assets	6,469,436	7,649,033
Total assets	7,833,159	9,660,781	$ 8,910,435
Current liabilities:
Accounts payable	475,215	525,560
Taxes payable	58,110	62,308
Dividends payable	25,461	45,245
Accrued compensation	85,512	59,470
Operating lease liabilities due within one year	22,884	21,307
Other accrued liabilities	181,471	156,031
Total current liabilities	1,075,733	1,479,603
Noncurrent liabilities:
Long-term debt	2,236,904	2,317,848
Operating lease liabilities	51,645	52,871
Other	199,675	180,603
Total noncurrent liabilities	3,852,193	4,594,049
Commitments and contingencies
Stockholders' equity:
Common stock Authorized - 500,000,000 shares, $1.00 par value Shares issued - 203,689,090 at December 31, 2023 and 204,162,814 at December 31, 2022	203,689	204,163
Other paid-in capital	1,466,235	1,466,037
Retained earnings	1,253,693	1,951,138
Accumulated other comprehensive loss	(18,384)	(30,583)
Treasury stock at cost - 538,921 shares at December 31, 2022	0	(3,626)
Total stockholders' equity	2,905,233	3,587,129
Total liabilities and stockholders' equity	7,833,159	9,660,781
MDU Resources Group, Inc.
Current assets:
Cash and cash equivalents	33,039	19,486	$ 6,159	$ 8,781
Receivables, net	6,568	4,410
Prepayments and other current assets	8,261	3,237
Total current assets	78,394	80,418
Noncurrent assets
Investments	37,722	50,206
Deferred income taxes	12,596	12,668
Operating lease right-of-use assets	31	72
Other	2,593	2,068
Total noncurrent assets	3,257,064	3,646,768
Total assets	3,335,458	3,727,186
Current liabilities:
Accounts payable	4,264	2,354
Taxes payable	542	572
Dividends payable	25,461	45,246
Accrued compensation	9,651	4,312
Operating lease liabilities due within one year	25	42
Other accrued liabilities	8,008	17,907
Total current liabilities	185,493	74,835
Noncurrent liabilities:
Long-term debt	189,048	0
Operating lease liabilities	6	30
Other	55,678	65,192
Total noncurrent liabilities	244,732	65,222
Commitments and contingencies
Stockholders' equity:
Common stock Authorized - 500,000,000 shares, $1.00 par value Shares issued - 203,689,090 at December 31, 2023 and 204,162,814 at December 31, 2022	203,689	204,163
Other paid-in capital	1,466,235	1,466,037
Retained earnings	1,253,693	1,951,138
Accumulated other comprehensive loss	(18,384)	(30,583)
Treasury stock at cost - 538,921 shares at December 31, 2022	0	(3,626)
Total stockholders' equity	2,905,233	3,587,129
Total liabilities and stockholders' equity	3,335,458	3,727,186
MDU Resources Group, Inc. | Subsidiaries
Current assets:
Receivables, net	30,526	53,285
Noncurrent assets
Investments	3,146,122	3,581,754
Notes receivable from subsidiaries	58,000	0
Current liabilities:
Accounts payable	3,435	4,402
Notes payable to subsidiaries	$ 134,107	$ 0