Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	2,792,911	1,431,503
Average price paid per share	$ 86.92	$ 75.87
Total cost	$ 242,748	$ 108,613
Stock repurchase program, repurchase authorization	5,000,000
Stock repurchase program, remaining number of shares authorized to be repurchased	3,137,219