Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	$ 1,596,610	$ 1,641,240
Other comprehensive income (loss), net of tax	6,977	23,107
Ending balance, Value	1,741,729	1,643,865
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	(118,441)
Other comprehensive income (loss) before reclassifications, net of tax	6,963
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0
Other comprehensive income (loss), net of tax	6,963
Ending balance, Value	(111,478)
Unrealized Gains (Losses) on Available-For-Sale Marketable Debt Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	2
Other comprehensive income (loss) before reclassifications, net of tax	14
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0
Other comprehensive income (loss), net of tax	14
Ending balance, Value	16
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	(118,439)	(93,497)
Other comprehensive income (loss) before reclassifications, net of tax	6,977
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0
Other comprehensive income (loss), net of tax	6,977	23,107
Ending balance, Value	$ (111,462)	$ (70,390)