Earnings Per Share - Summary of Earnings Per Share, Basic and Diluted (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 73,099	$ 54,401	$ 137,761	$ 96,480
Weighted-average shares outstanding	81,111	82,430	80,912	82,054
Share-based payment awards classified as participating securities	462	864	486	875
Denominator for basic earnings per share	81,573	83,294	81,398	82,929
Dilutive securities	2,888	2,443	2,814	2,522
Denominator for diluted earnings per share	84,461	85,737	84,212	85,451
Basic earnings per share	$ 0.90	$ 0.65	$ 1.69	$ 1.16
Diluted earnings per share	$ 0.87	$ 0.63	$ 1.64	$ 1.13