Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	$ 1,741,729	$ 1,596,610	$ 1,643,865	$ 1,641,240	$ 1,596,610	$ 1,641,240
Other comprehensive income (loss), net of tax	(10,564)	6,977	(29,721)	23,107	(3,587)	(6,614)
Ending balance, Value	1,722,951	1,741,729	1,599,594	1,643,865	1,722,951	1,599,594
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value		(118,441)			(118,441)
Other comprehensive income (loss) before reclassifications, net of tax					(3,638)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax					0
Other comprehensive income (loss), net of tax					(3,638)
Ending balance, Value	(122,079)				(122,079)
Unrealized Gains (Losses) on Available-For-Sale Marketable Debt Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value		2			2
Other comprehensive income (loss) before reclassifications, net of tax					51
Amounts reclassified from accumulated other comprehensive income (loss), net of tax					0
Other comprehensive income (loss), net of tax					51
Ending balance, Value	53				53
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance, Value	(111,462)	(118,439)	(70,390)	(93,497)	(118,439)	(93,497)
Other comprehensive income (loss) before reclassifications, net of tax					(3,587)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax					0
Other comprehensive income (loss), net of tax	(10,564)	6,977	(29,721)	23,107	(3,587)
Ending balance, Value	$ (122,026)	$ (111,462)	$ (100,111)	$ (70,390)	$ (122,026)	$ (100,111)