Stockholders' Equity - Schedule of Accumulated Other Comprehensive Income Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	$ 1,580,664	$ 1,786,901	$ 1,895,692
Other comprehensive income (loss)	35,197	(76,306)	(23,213)
Ending balance, Value	1,641,240	1,580,664	1,786,901
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	(128,671)	(52,261)
Other comprehensive income (loss) before reclassifications, net of tax	35,352	(76,410)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0
Other comprehensive income (loss)	35,352	(76,410)
Ending balance, Value	(93,319)	(128,671)	(52,261)
Unrealized Gains (Losses) on Available-for-Sale Marketable Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	(23)	(127)
Other comprehensive income (loss) before reclassifications, net of tax	(155)	104
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0
Other comprehensive income (loss)	(155)	104
Ending balance, Value	(178)	(23)	(127)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	(128,694)	(52,388)	(29,175)
Other comprehensive income (loss) before reclassifications, net of tax	35,197	(76,306)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0
Other comprehensive income (loss)	35,197	(76,306)	(23,213)
Ending balance, Value	$ (93,497)	$ (128,694)	$ (52,388)