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
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 75,109	$ 64,662
Denominator for basic earnings per share	82,737	81,222
Dilutive securities	2,958	2,738
Denominator for diluted earnings per share	85,695	83,960
Basic earnings per share	$ 0.91	$ 0.80
Diluted earnings per share	$ 0.88	$ 0.77