Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Equity [Abstract]
Purchase of common stock, Shares	(5)	(294)
Stock option exercises, Shares	355	265
Employee stock plan purchases, Shares	23	26
Shares issued for acquisition, Shares	13
Purchase of common stock, Amount	$ (645)	$ (22,815)
Stock option exercises, Amount	6,729	4,117
Employee stock plan purchases, Amount	2,243	$ 2,014
Shares issued for acquisition, Amount	$ 1,519