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Major classes of assets and liabilities (Details 4) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Current assets: |  |  |  |
Total current assets held for sale |  | $ 479 |  | $ 14,391
Current liabilities: |  |  |  |
Total current liabilities held for sale |  | 11,993 |  | 9,924
Refining [Member] | Discontinued operations, held-for-sale or disposed by sale [Member] |  |  |  |
Current assets: |  |  |  |
Income taxes receivable |  | 1,778 |  | 13,987
Total current assets held for sale |  | 1,778 |  | 13,987
Total assets held for sale |  | 1,778 | [1] | 13,987
Current liabilities: |  |  |  |
Accounts payable |  | 0 |  | 7,425
Total current liabilities held for sale |  | 0 |  | 7,425
Deferred credits and other liabilities: |  |  |  |
Deferred income taxes (b) | [2] | 37 |  | 14
Total noncurrent liabilities held for sale |  | 37 |  | 14
Total liabilities held for sale |  | $ 37 |  | $ 7,439
[1] | On the Company's Consolidated Balance Sheets, these amounts were reclassified to current income taxes payable and are reflected in current liabilities held for sale.
[2] | On the Company's Consolidated Balance Sheets, these amounts were reclassified to noncurrent deferred income tax assetsand are reflected in noncurrent assets held for sale.

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