Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	10 Months Ended	12 Months Ended
	Oct. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Product Information [Line Items]
Advertising expenses		$ 1,100,000	$ 900,000	$ 800,000
Selling, general and administrative expenses		149,544,000	131,375,000	111,402,000
Other income		4,875,000	3,981,000	1,379,000
Operating revenue		2,849,685,000	2,854,390,000	2,699,250,000
Income from equity method investments		12,185,000	4,946,000	5,900,000
Interest in assets of joint venture		0	1,800,000
Investment in equity method investments		14,300,000	6,200,000
Income from equity method investments		12,200,000	5,000,000.0	5,900,000
Cash, cash equivalents and restricted cash		86,012,000	1,567,000	2,112,000	$ 668,000
Restricted cash		16,100,000	0
Impairment of intangible assets, excluding goodwill		0	0	0
Self-insured limit		5,000,000
Deductible threshold		1,500,000
Stop loss limit		1,000,000
Manufactured equipment held for resale and/or rental
Product Information [Line Items]
Inventories		36,900,000	37,200,000
Materials and supplies
Product Information [Line Items]
Inventories, materials and supplies		$ 6,800,000	5,500,000
RSUs
Product Information [Line Items]
Award vesting period		3 years
MDU Resources | RSUs
Product Information [Line Items]
Award vesting period	3 years
Related party
Product Information [Line Items]
Other income		$ 47,000
Related party | Allocated corporate expenses
Product Information [Line Items]
General corporate expenses		30,400,000	27,100,000	21,200,000
Joint ventures
Product Information [Line Items]
Operating revenue		600,000	7,800,000	14,800,000
Income from equity method investments		$ 200,000	$ 2,100,000	$ 3,000,000.0