Income Taxes - Summary of Differences Between Income Tax Expense Computed at Statutory Federal Income Tax Rate and Per Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax expense at federal rate of 21% (35% pre-2018)									$ 19,278	$ 15,250	$ 64,953
State income taxes, net of federal benefit									5,246	(2,238)	7,060
Change in valuation allowance									12,657	(1,884)	(8,524)
Foreign tax rate differential									(4,796)	(15,622)	(11,830)
Unrecognized tax benefit increase									1,262	3,007	1,045
Tax effect of foreign operations									8,546	5,532	5,988
Tax benefit of research & development									(2,557)	(1,904)	(1,088)
Transition tax									(8,112)	20,867
Revaluation of deferred tax balances									(4,937)	14,953
Performance-based compensation									(4,541)	2,081
Domestic production activities										(3,793)	(700)
Other									832	2,188	(858)
Income tax provision	$ 21,054	$ 2,012	$ 3,764	$ (3,952)	$ 65,758	$ (2,233)	$ (20,914)	$ (4,174)	$ 22,878	$ 38,437	$ 56,046