Schedule I-Condensed Financial Information of Registrant - Condensed Statements of Income and Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Total external operating revenues	$ 4,614,457	$ 4,401,264	$ 3,402,191
Operating expenses	4,231,362	4,071,785	3,123,385
Operating income	425,978	369,999	331,051
Realized gain on tax-free exchange of the retained shares in Knife River	186,556	0	0
Interest expense	114,308	80,698	70,709
Income before income taxes	539,898	300,529	286,066
Income taxes	59,473	49,761	43,544
Income from continuing operations	480,425	250,768	242,522
Discontinued operations, net of tax	(65,718)	116,721	135,609
Net income	414,707	367,489	378,131
Comprehensive income attributable to common stockholders	414,600	377,910	385,205
MDU Resources Group, Inc.
Condensed Financial Statements, Captions [Line Items]
Total external operating revenues	0	0	0
Operating expenses	14,959	4,888	0
Operating income	(14,959)	(4,888)	0
Realized gain on tax-free exchange of the retained shares in Knife River	186,556	0	0
Interest expense	16,099	0	0
Income before income taxes	155,498	(4,888)	0
Income taxes	(7,705)	(1,193)	0
Equity in earnings of subsidiaries from continuing operations	317,222	254,463	242,522
Income from continuing operations	480,425	250,768	242,522
Equity in earnings (loss) of subsidiaries from discontinued operations	(17,922)	125,726	135,609
Discontinued operations, net of tax	(47,796)	(9,005)	0
Net income	414,707	367,489	378,131
Comprehensive income attributable to common stockholders	$ 414,600	$ 377,910	$ 385,205