Schedule I - Condensed Financial Information of Registrant - Condensed Balance Sheets - Parenthetical (Details) - $ / shares	Dec. 31, 2024	Dec. 31, 2023
Condensed Financial Statements, Captions [Line Items]
Common stock, authorized (in shares)	500,000,000	500,000,000
Common stock, par value per share (in usd per share)	$ 1.00	$ 1.00
Common stock, issued (in shares)	203,934,578	203,689,090
MDU Resources Group, Inc.
Condensed Financial Statements, Captions [Line Items]
Common stock, authorized (in shares)	500,000,000	500,000,000
Common stock, par value per share (in usd per share)	$ 1.00	$ 1.00
Common stock, issued (in shares)	203,934,578	203,689,090