Earnings Per Share - Summary of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 114,185	$ 98,678	$ 224,157	$ 192,831
Denominator for basic and diluted earnings per share:
Denominator for basic earnings per share (in shares)	92,665	91,904	92,591	91,828
Dilutive securities (in shares)	1,884	2,146	1,846	2,164
Denominator for diluted earnings per share (in shares)	94,549	94,050	94,437	93,992
Basic earnings per share (in dollars per share)	$ 1.23	$ 1.07	$ 2.42	$ 2.10
Diluted earnings per share (in dollars per share)	$ 1.21	$ 1.05	$ 2.37	$ 2.05