Summary of Differences Between Income Tax Expense Computed at Statutory Federal Income Tax Rate and Per Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax expense at federal rate of 35%									$ 39,680	$ 34,569	$ 32,606
State income taxes, net of federal benefit									(2,462)	(544)	675
Change in valuation allowance									(9,066)	3,521	(1,615)
Foreign tax rate differential									(5,710)	(5,508)	(4,650)
Unrecognized tax benefit increase									2,977	65	488
Tax effect of foreign operations									261	(104)	5,906
Acquisition Costs										289	896
Tax benefit of research & development									(871)	(3,446)	(4,001)
Other									3,128	2,367	(1,014)
Income tax provision	$ 18,856	$ 3,786	$ 5,825	$ (530)	$ 23,334	$ 9,433	$ 2,409	$ (3,967)	$ 27,937	$ 31,209	$ 29,291