Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Stock option exercises, Shares	1,118	855	1,443
Purchases of common stock, Shares	(5)	(294)
Employee stock plan purchases, Shares	43	53	64
Shares issued for acquisitions, Shares	2,149	17
Stock option exercises, Amount	$ 23,160	$ 14,680	$ 18,289
Purchases of common stock	(645)	(22,817)
Employee stock plan purchases, Amount	4,671	4,144	$ 3,542
Shares issued for acquisitions, Amount	$ 364,333	$ 1,473