Related Party Transactions - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Related Party Transaction [Line Items]
General corporate expenses				$ 21,500,000
Operating lease cost	$ 8,156,000	$ 6,693,000	$ 22,769,000	19,448,000
Related party
Related Party Transaction [Line Items]
General corporate expenses	4,900,000	4,500,000	27,600,000	21,500,000
Operating lease cost	200,000	200,000	500,000	500,000
Cash management and financing program | Related party
Related Party Transaction [Line Items]
Interest expense	3,000,000	4,700,000	9,100,000	13,500,000
MDU Resources, Services, Sales, and Rental Transactions | Related party
Related Party Transaction [Line Items]
Related party transaction	$ 0	$ 0	$ 300,000	$ 300,000