Income Taxes - Geographic Source of Income Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S.	$ 122,801	$ (124,154)	$ (99,738)
Other than U.S.	137,358	206,469	164,348
Income before provision for income taxes	$ 260,159	$ 82,315	$ 64,610