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Discontinued operations - Schedule of Assets and Liabilities of Discontinued Operations (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2023 | Sep. 30, 2022
--- | --- | --- | --- | ---
Current assets: |  |  |  |
Cash and cash equivalents |  |  | $ 7,200 |
Noncurrent assets: |  |  |  |
Total noncurrent assets of discontinued operations | $ 0 | $ 0 | 1,687,611 |
Current liabilities: |  |  |  |
Total current liabilities of discontinued operations | 0 | 0 | 448,715 |
Noncurrent liabilities: |  |  |  |
Total noncurrent liabilities of discontinued operations | $ 0 | $ 0 | $ 897,085 |
Knife River Corporation | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff |  |  |  |
Current assets: |  |  |  |
Cash and cash equivalents |  |  |  | $ 7,218
Receivables, net |  |  |  | 205,564
Inventories |  |  |  | 373,215
Prepayments and other current assets |  |  |  | 34,899
Total current assets of discontinued operations |  |  |  | 620,896
Noncurrent assets: |  |  |  |
Net property, plant and equipment |  |  |  | 1,317,368
Goodwill |  |  |  | 274,540
Other intangible assets, net |  |  |  | 12,763
Investments |  |  |  | 35,542
Operating lease right-of-use assets |  |  |  | 43,995
Other |  |  |  | 3,403
Total noncurrent assets of discontinued operations |  |  |  | 1,687,611
Total assets of discontinued operations |  |  |  | 2,308,507
Current liabilities: |  |  |  |
Short-term borrowings |  |  |  | 208,000
Long-term debt due within one year |  |  |  | 30,211
Accounts payable |  |  |  | 118,175
Taxes payable |  |  |  | (1,402)
Accrued compensation |  |  |  | 14,010
Operating lease liabilities due within one year |  |  |  | 12,981
Other accrued liabilities |  |  |  | 66,740
Total current liabilities of discontinued operations |  |  |  | 448,715
Noncurrent liabilities: |  |  |  |
Long-term debt |  |  |  | 577,138
Deferred income taxes |  |  |  | 175,062
Asset retirement obligations |  |  |  | 33,462
Operating lease liabilities |  |  |  | 31,014
Other |  |  |  | 80,409
Total noncurrent liabilities of discontinued operations |  |  |  | 897,085
Total liabilities of discontinued operations |  |  |  | $ 1,345,800

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