Schedule I - Condensed Financial Information of Registrant - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 66,904	$ 60,473
Receivables, net	274,303	250,153
Prepayments and other current assets	64,676	66,431
Total current assets	666,259	1,363,723
Noncurrent assets
Investments	115,459	112,475
Other	244,722	211,369
Total noncurrent assets	6,372,559	6,469,436
Total assets	7,038,818	7,833,159	$ 9,660,781
Current liabilities:
Accounts payable	150,070	159,975
Taxes payable	43,372	49,553
Dividends payable	26,511	25,461
Accrued compensation	35,264	40,792
Other accrued liabilities	124,514	129,592
Total current liabilities	678,598	1,075,733
Noncurrent liabilities:
Long-term debt, net of debt issuance costs	2,130,910	2,104,904
Other	231,895	209,882
Total noncurrent liabilities	3,669,646	3,852,193
Commitments and contingencies
Stockholders' equity:
Common stock Authorized - 500,000,000 shares, $1.00 par value Shares issued - 203,934,578 at December 31, 2024 and 203,689,090 at December 31, 2023	203,935	203,689
Other paid-in capital	1,473,738	1,466,235
Retained earnings	1,029,699	1,253,693
Accumulated other comprehensive loss	(16,798)	(18,384)
Total stockholders' equity	2,690,574	2,905,233	3,587,129	$ 3,382,874
Total liabilities and stockholders' equity	7,038,818	7,833,159
MDU Resources Group, Inc.
Current assets:
Cash and cash equivalents	29,361	33,039	$ 19,486	$ 6,159
Receivables, net	2,777	6,568
Taxes receivable	5,799	0
Prepayments and other current assets	3,210	8,261
Total current assets	73,102	78,394
Noncurrent assets
Investments	37,264	37,722
Deferred income taxes	13,569	12,596
Operating lease right-of-use assets	160	31
Other	2,874	2,593
Total noncurrent assets	2,915,178	3,257,064
Total assets	2,988,280	3,335,458
Current liabilities:
Accounts payable	4,076	4,264
Taxes payable	0	542
Dividends payable	26,511	25,461
Accrued compensation	7,939	9,651
Operating lease liabilities due within one year	60	25
Other accrued liabilities	7,653	8,008
Total current liabilities	245,351	185,493
Noncurrent liabilities:
Long-term debt, net of debt issuance costs	(536)	57,048
Operating lease liabilities	100	6
Other	52,791	187,678
Total noncurrent liabilities	52,355	244,732
Commitments and contingencies
Stockholders' equity:
Common stock Authorized - 500,000,000 shares, $1.00 par value Shares issued - 203,934,578 at December 31, 2024 and 203,689,090 at December 31, 2023	203,935	203,689
Other paid-in capital	1,473,738	1,466,235
Retained earnings	1,029,699	1,253,693
Accumulated other comprehensive loss	(16,798)	(18,384)
Total stockholders' equity	2,690,574	2,905,233
Total liabilities and stockholders' equity	2,988,280	3,335,458
MDU Resources Group, Inc. | Subsidiaries
Current assets:
Receivables, net	31,955	30,526
Noncurrent assets
Investments	2,861,311	3,146,122
Notes receivable from subsidiaries	0	58,000
Current liabilities:
Accounts payable	1,077	3,435
Notes payable to subsidiaries	$ 198,035	$ 134,107