Earnings Per Share - Schedule of EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Basic:
Net Income	$ 236,250	$ 223,784	$ 144,177	$ 154,256
Less: Net income allocable to participating RSUs	610	1,036	1,628	2,393
Net income available for basic common shares	$ 235,640	$ 222,748	$ 142,549	$ 151,863
Weighted average common shares outstanding	341,961	339,420	341,089	338,954
Basic net income per common share (in USD per share)	$ 0.69	$ 0.66	$ 0.42	$ 0.45
Diluted:
Net Income	$ 236,250	$ 223,784	$ 144,177	$ 154,256
Less: Net income allocable to participating RSUs	609	1,035	1,628	2,393
Net income available for diluted common shares	$ 235,641	$ 222,749	$ 142,549	$ 151,863
Weighted average common shares outstanding	341,961	339,420	341,089	338,954
Weighted average common equivalent shares arising from:
Dilutive stock options and non-participating RSUs (in shares)	2,265	370	2,209	590
Weighted average number of common and potential common shares	344,226	339,790	343,298	339,544
Diluted net income per common share (in USD per share)	$ 0.68	$ 0.66	$ 0.42	$ 0.45
Nonqualified stock options and non-participating RSUs excluded from the calculation of diluted net income per common share (in shares)	9,800	14,900	7,700	8,600