Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Stock option exercises, Shares	827	1,118	855
Purchases of common stock, Shares		(5)	(294)
Employee stock plan purchases, Shares		43	53
Shares issued for acquisitions, Shares	0	2,149	17
Stock option exercises, Amount		$ 23,160	$ 14,680
Purchases of common stock, Amount	$ (112,699)	(645)	(22,817)
Employee stock plan purchases, Amount	6,236	4,671	4,144
Shares issued for acquisitions, Amount	$ 0	$ 364,333	$ 1,473