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Income Taxes (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Components of the provision for income taxes |  |  |
Federal | $ (3,826) | $ 0 | $ 5,698
State | 1,618 | 1,662 | 3,398
Deferred portion of income tax expense (benefit) | (41,835) | 141,708 | (192,066)
Income tax expense (benefit) | $ (44,043) | $ 143,370 | $ (182,970)
Effective tax rate (as a percent) | 19.10% | 22.00% | 53.20%
Deferred income taxes [Abstract] |  |  |
Deferred tax liabilities, oil and gas properties | $ 205,028 | $ 218,094 |
Deferred tax liabilities, derivatives assets | 4,646 | 35,247 |
Deferred tax liabilities, other | 12,361 | 4,812 |
Total deferred tax liabilities | 222,035 | 258,153 |
Deferred tax assets, credit carryover | 11,270 | 22,554 |
Deferred tax assets, pension | 5,971 | 6,427 |
Deferred tax assets, federal and state tax net operating loss carryovers | 4,172 | 4,217 |
Deferred tax assets, stock compensation | 3,503 | 3,263 |
Deferred tax assets, other liabilities | 10,803 | 1,497 |
Total deferred tax assets | 35,719 | 37,958 |
Deferred tax assets, valuation allowance | (3,070) | (3,083) |
Net deferred tax assets | 32,649 | 34,875 |
Total net deferred tax liabilities | 189,386 | 223,278 |
State and local jurisdiction [Member] |  |  |
Deferred income taxes [Abstract] |  |  |
Current state income tax payable | 1,404 | 1,331 |
Net operating loss carryforwards | 77,800 |  |
Internal Revenue Service (IRS) [Member] | Domestic tax authority [Member] |  |  |
Deferred income taxes [Abstract] |  |  |
Current federal income tax refundable | 3,885 | $ 59 |
Net operating loss carryforwards | 3,300 |  |
Internal Revenue Service (IRS) [Member] | Research and development tax credit carryforward [Member] | Domestic tax authority [Member] |  |  |
Deferred income taxes [Abstract] |  |  |
Tax credit carryforwards | 7,400 |  |
Internal Revenue Service (IRS) [Member] | Alternative minimum tax credit carryforward [Member] | Domestic tax authority [Member] |  |  |
Deferred income taxes [Abstract] |  |  |
Tax credit carryforwards | $ 4,300 |  |

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