Calculation of Net Income Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 61,551	$ 55,863
Income allocated to participating securities-basic		2
Net income available to common stockholders-basic	61,551	55,861
Basic weighted average shares	135,333	137,311
Basic net income per share	$ 0.45	$ 0.41
Net income	61,551	55,863
Income allocated to participating securities-diluted		2
Net income available to common stockholders-diluted	$ 61,551	$ 55,861
Basic weighted average shares	135,333	137,311
Dilutive effect of potential common shares	828	1,083
Diluted weighted average shares	136,161	138,394
Diluted net income per share	$ 0.45	$ 0.40