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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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