Income Taxes - Domestic and Foreign Components of Income (loss) Before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 123,696	$ 118,871	$ 87,803
Foreign	241,103	123,695	98,298
Net income before provision for income taxes and equity in losses of investee	$ 364,799	$ 242,566	$ 186,101