Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Purchases of common stock, Shares	(758)	(5)
Stock option exercises, Shares	564	420
Employee stock plan purchases, Shares	34	33
Shares issued for acquisition, Shares		13
Purchases of common stock, Amount	$ (94,499)	$ (645)
Stock option exercises, Amount	15,089	8,369
Employee stock plan purchases, Amount	$ 4,429	3,367
Shares issued for acquisition, Amount		$ 1,519