Changes in Accumulated Other Comprehensive Loss - Changes in Accumulated and Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ 968,435
Ending balance	$ 994,768		994,768
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(40,917)	$ (41,650)	(35,610)	$ (53,171)
Other comprehensive (loss) income before reclassifications, net of income tax	419	5,297	(4,888)	16,818
Net current-period other comprehensive (loss) income	419	5,297	(4,888)	16,818
Ending balance	(40,498)	(36,353)	(40,498)	(36,353)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,120	(378)	(208)	932
Other comprehensive (loss) income before reclassifications, net of income tax	217	(281)	1,188	(1,077)
Amounts reclassified from accumulated other comprehensive loss to the condensed consolidated statement of operations and comprehensive income, net of income tax	(192)	229	165	(285)
Net current-period other comprehensive (loss) income	25	(52)	1,353	(1,362)
Ending balance	1,145	(430)	1,145	(430)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(39,797)	(42,028)	(35,818)	(52,239)
Other comprehensive (loss) income before reclassifications, net of income tax	636	5,016	(3,700)	15,741
Amounts reclassified from accumulated other comprehensive loss to the condensed consolidated statement of operations and comprehensive income, net of income tax	(192)	229	165	(285)
Net current-period other comprehensive (loss) income	444	5,245	(3,535)	15,456
Ending balance	$ (39,353)	$ (36,783)	$ (39,353)	$ (36,783)