Discontinued operations - Schedule of Income and Expense Constituting Pretax Income (Loss) From Discontinued Operations (Details) - Knife River Corporation - Discontinued Operations, Disposed of by Means Other than Sale, Spinoff $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	$ 307,239
Operating expenses	351,274
Operating loss	(44,035)
Other income	493
Interest expense	14,067
Loss from discontinued operations before income taxes	(57,609)
Income taxes	(12,087)
Discontinued operations, net of tax	$ (45,522)