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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 78,620	$ 59,648	$ 216,381	$ 156,128
Denominator for basic earnings per share	81,974	84,002	81,592	83,260
Dilutive securities	2,931	2,222	2,854	2,421
Denominator for diluted earnings per share	84,905	86,224	84,446	85,681
Basic earnings per share	$ 0.96	$ 0.71	$ 2.65	$ 1.88
Diluted earnings per share	$ 0.93	$ 0.69	$ 2.56	$ 1.82