Discontinued Operations - Schedule of Assets and Liabilities of Discontinued Operations (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents		$ 10,100	$ 10,400
Noncurrent assets:
Noncurrent assets of discontinued operations	$ 0	1,685,751
Current liabilities:
Total current liabilities of discontinued operations	0	496,923
Noncurrent liabilities:
Total noncurrent liabilities of discontinued operations	$ 0	765,904
Knife River Corporation | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Current assets:
Cash and cash equivalents		10,090
Receivables, net		241,302
Inventories		323,277
Prepayments and other current assets		17,848
Total current assets of discontinued operations		592,517
Noncurrent assets:
Net property, plant and equipment		1,315,213
Goodwill		274,540
Other intangible assets, net		13,430
Investments		33,086
Operating lease right-of-use assets		45,872
Other		3,610
Noncurrent assets of discontinued operations		1,685,751
Total assets of discontinued operations		2,278,268
Current liabilities:
Short-term borrowings		208,000
Long-term debt due within one year		30,211
Accounts payable		131,608
Taxes payable		8,502
Accrued compensation		29,192
Operating lease liabilities due within one year		13,210
Other accrued liabilities		76,200
Total current liabilities of discontinued operations		496,923
Noncurrent liabilities:
Long-term debt		445,546
Deferred income taxes		175,804
Asset retirement obligations		33,015
Operating lease liabilities		32,663
Other		78,876
Total noncurrent liabilities of discontinued operations		765,904
Total liabilities of discontinued operations		$ 1,262,827