Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components Of Income Tax Expense Benefit [Line Items]
Current, Federal	$ 60,529	$ 7,759	$ 4,170
Current, State	808	(10)	528
Current, Foreign	36,700	31,387	18,817
Current, Total	98,037	39,136	23,515
Deferred (net of valuation allowance), Federal	249	(8,183)	(11,374)
Deferred (net of valuation allowance), State	(891)	250	(738)
Deferred (net of valuation allowance), Foreign	2,270	(8,351)	(1,201)
Deferred Income Tax Expense (Benefit)	1,628	(16,284)	(13,313)
Income tax expense	$ 99,665	$ 22,852	$ 10,202