Shareholders' Equity - Summary of Activities in Common Stock (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Stock option exercises, Shares	855	1,443	1,218
Treasury stock purchases, shares	(294)
Employee stock plan purchases, Shares	53	64	81
Shares issued for acquisition, Shares	17		60
Stock option exercises, Amount	$ 14,680	$ 18,289	$ 12,443
Treasury stock purchases	(22,817)
Employee stock plan purchases, Amount	4,144	3,542	2,641
Shares issued for acquisition, Amount	$ 1,473		$ 2,815