Significant Accounting Policies - Electric Fuel and Purchased Power Deferral (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Electric fuel and purchased power costs recoverable	$ 33.9	$ 2.7
Electric fuel and purchased power costs refundable		$ 4.9

Long-Term Contract for Purchase of Electric Power, Recoverable

No definition available.

Name:	mdu_LongTermContractForPurchaseOfElectricPowerRecoverable
Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant