Discontinued Operations - Narrative (Details) $ in Thousands, shares in Millions			3 Months Ended	12 Months Ended
	May 31, 2023 shares	Apr. 25, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt			$ 2,298,223	$ 2,298,223	$ 2,365,667
Repayments of long-term debt				$ 792,998	$ 65,764	$ 24,758
Restructuring, Incurred Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]				Less: income (loss) from discontinued operations, net of tax	Less: income (loss) from discontinued operations, net of tax
Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of long-term debt		$ 825,000
Knife River Corporation | Revolving Credit Facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Line of credit facility, maximum borrowing capacity		350,000
Knife River Corporation | Term Loan Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt instrument, face amount		275,000
Senior Notes | Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt		$ 425,000
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pro rata distribution of shares, percentage	0.90
Stock split, conversion ratio	4
Retained ownership percentage	0.10
Number of retained shares (in shares) | shares	5.7
Gain on exchange of retained shares			$ 186,600
Separation related costs				$ 47,800	$ 9,000
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Knife River Corporation | Cash Received, TSA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation, amount of continuing cash flows after disposal				2,900
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Knife River Corporation | Cash Paid, TSA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation, amount of continuing cash flows after disposal				$ 823