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Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 | Dec. 31, 2017 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Income Tax [Line Items] |  |  |  |  |  |  |
Tax at statutory rate |  |  |  | 21.00% | 21.00% | 35.00% |
Effective tax rate |  |  |  | 7.40% | 27.17% | 20.80% |
Effective income tax rate reconciliation nondeductible portion of goodwill impairment charge | $ 213,700 |  |  |  |  |  |
Income tax benefit resulting from the reduction of deferred tax liabilities |  | $ (70,000) |  |  |  |  |
Increase (decrease) in net deferred tax liability |  |  |  | $ 178,100 |  |  |
Income tax expense for excess tax deficiencies |  |  |  | 3,900 | $ 1,400 | $ 200 |
Net operating loss carryforwards for federal and state tax |  | 114,500 |  | 75,400 | 100,700 | 114,500 |
Operating loss carryforwards subject to expiration |  |  |  |  | 38,700 |  |
Operating loss carryforwards not subject to expiration |  |  |  |  | 36,700 |  |
Uncertain tax position liability |  | $ 10,972 |  | 7,409 | 11,185 | $ 10,972 | $ 9,469
Unrecognized tax benefits that would impact effective tax rate |  |  |  |  | 7,100 |  |
Increase (decrease) in uncertain tax position |  |  |  | 3,800 | 200 |  |
Company's accrued liability for interest and penalties related to income tax liabilities |  |  |  | 600 | 1,100 |  |
Deferred tax assets |  |  |  | 104,390 |  |  |
Net deferred tax liabilities |  |  |  |  | $ 73,671 |  |
Capital losses incurred |  |  |  | $ 68,000 |  |  |
Capital loss carryforwards, expiration date |  |  |  | 2024 |  |  |
Capital loss carryforwards, valuation allowance |  |  |  | $ 17,100 |  |  |
Earliest Tax Year [Member] |  |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |  |
Federal and state income tax examinations |  |  |  | 2015 |  |  |
Latest Tax Year [Member] |  |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |  |
Federal and state income tax examinations |  |  |  |  | 2018 |  |
Scenario, Forecast [Member] |  |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |  |
Increase (decrease) in uncertain tax position |  |  | $ 2,000 |  |  |  |
Minimum [Member] |  |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |  |
Expiration period of operating loss carryforwards |  |  |  | 2021 |  |  |
Maximum [Member] |  |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |  |
Expiration period of operating loss carryforwards |  |  |  | 2039 |  |  |

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