Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Provisional income tax expense (benefit)	$ (128,200)
Provisional income tax benefit due to corporate rate reduction	210,000
Transition tax	81,800
Change in tax rate effect on deferred tax asset	$ 210,000
Income tax expense at federal statutory rate, rate	35.00%	35.00%	35.00%
Valuation allowance	$ 59,349	$ 76,395
Increase (decrease) in the total valuation allowance	(17,000)	13,800
Net operating loss carryforwards for state income tax purposes	590,000
Federal operating loss carry forwards	44,000
Accrued interest and penalties related to the unrecognized tax benefits	1,300	5,900
Total unrecognized tax benefits	31,558	$ 26,155	$ 21,834	$ 18,641
Unrecognized tax benefits that would affect effective tax rate	$ 31,600