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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 88,549	$ 73,099	$ 163,658	$ 137,761
Denominator for basic and diluted earnings per share:
Denominator for basic earnings per share	82,996	81,573	82,867	81,398
Dilutive securities	2,821	2,888	2,890	2,814
Denominator for diluted earnings per share	85,817	84,461	85,757	84,212
Basic earnings per share	$ 1.07	$ 0.90	$ 1.97	$ 1.69
Diluted earnings per share	$ 1.03	$ 0.87	$ 1.91	$ 1.64