Long-term debt outstanding (Details 2) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2022	May 31, 2023	Dec. 31, 2022
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,247,422	$ 2,247,422	$ 2,090,200		$ 2,365,667
Long-term debt due within one year	1,319	1,319	86,319		47,819
Long-term debt	2,246,103	2,246,103	2,003,881		2,317,848
Repayments of Long-term Debt		506,191	147,397
Senior Notes
Long-term debt outstanding [Line Items]
Long-term debt	$ 1,757,000	$ 1,757,000	1,847,000		1,848,500
Weighted Average Interest Rate	4.33%	4.33%
Term Loan Agreements
Long-term debt outstanding [Line Items]
Long-term debt	$ 382,000	$ 382,000	7,700		7,000
Weighted Average Interest Rate	6.46%	6.46%
Commercial Paper
Long-term debt outstanding [Line Items]
Long-term debt	$ 58,900	$ 58,900	175,020		349,050
Weighted Average Interest Rate	5.70%	5.70%
Medium-term Notes
Long-term debt outstanding [Line Items]
Long-term debt	$ 35,000	$ 35,000	35,000		35,000
Weighted Average Interest Rate	7.32%	7.32%
Credit Agreements
Long-term debt outstanding [Line Items]
Long-term debt	$ 20,300	$ 20,300	29,860		130,000
Weighted Average Interest Rate	8.35%	8.35%
Other Notes
Long-term debt outstanding [Line Items]
Long-term debt	$ 987	$ 987	1,621		1,614
Weighted Average Interest Rate	2.24%	2.24%
Long-term Debt
Long-term debt outstanding [Line Items]
Unamortized Debt Issuance Costs	$ 6,765	$ 6,765	5,406		5,211
Discount	0	$ 0	$ 595		$ 286
Long-term Debt | Centennial Energy Holdings, Inc.
Long-term debt outstanding [Line Items]
Repayments of Long-term Debt	$ 455,000
Revolving Credit Facility | MDU Resources Group, Inc.
Long-term debt outstanding [Line Items]
Long-term debt				$ 200,000
Ratio of total debt to total capitalization as specified in debt covenants				65.00%
Term Loan Agreement | MDU Resources Group, Inc.
Long-term debt outstanding [Line Items]
Long-term debt				$ 375,000
Ratio of total debt to total capitalization as specified in debt covenants				65.00%