Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Purchases of common stock, Shares	(758)	(5)
Stock option exercises, Shares	241	355
Employee stock plan purchases, Shares	23	23
Shares issued for acquisition, Shares		13
Purchases of common stock, Amount	$ (94,497)	$ (645)
Stock option exercises, Amount	5,793	6,729
Employee stock plan purchases, Amount	$ 2,818	2,243
Shares issued for acquisition, Amount		$ 1,519