Earnings Per Share - Summary of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 116,770	$ 95,509	$ 309,601	$ 259,167
Denominator for basic and diluted earnings per share:
Denominator for basic earnings per share	92,110	83,611	91,923	83,118
Dilutive securities	2,047	2,523	2,146	2,570
Denominator for diluted earnings per share	94,157	86,134	94,069	85,688
Basic earnings per share	$ 1.27	$ 1.14	$ 3.37	$ 3.12
Diluted earnings per share	$ 1.24	$ 1.11	$ 3.29	$ 3.02