Income Taxes - Schedule of Provision for Taxes on Income and Other Related Income Before Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal
Current									$ 32,299	$ 18,811	$ 7,697
Deferred									(1,744)	(3,192)	3,890
State
Current									1,764	2,273	1,559
Deferred									192	(1,171)	(225)
Foreign
Current									13,077	14,960	14,562
Deferred									2,102	(4,063)	(664)
Total									47,690	27,618	26,819
Income before Taxes
Domestic									72,662	64,675	48,721
Foreign									66,575	49,141	54,135
Income Before Provision for Income Taxes	$ 28,532	$ 29,312	$ 37,063	$ 44,330	$ 7,009	$ 27,143	$ 39,196	$ 40,468	$ 139,237	$ 113,816	$ 102,856