Earnings Per Share - Summary of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 109,972	$ 94,153
Denominator for basic and diluted earnings per share:
Denominator for basic earnings per share (in shares)	92,516	91,750
Dilutive securities (in shares)	1,813	2,184
Denominator for diluted earnings per share (in shares)	94,329	93,934
Basic earnings per share (in dollars per share)	$ 1.19	$ 1.03
Diluted earnings per share (in dollars per share)	$ 1.17	$ 1.00