Net Income Per Share - Summary of Table Reconciling Basic and Diluted Net Income Per Share (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
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Basic Earnings Per Share, Net income	$ 23,948	$ 19,737	$ 76,371	$ 68,666
Basic Earnings Per Share, Weighted average common shares outstanding	100,645	95,690	100,901	94,886
Basic Earnings Per Share	$ 0.24	$ 0.20	$ 0.76	$ 0.72
Diluted Earnings Per Share, Weighted average common shares outstanding	100,645	95,690	100,901	94,886
Diluted Earnings Per Share, Weighted average common shares outstanding	101,131	96,125	101,351	95,274
Diluted Earnings Per Share	$ 0.23	$ 0.20	$ 0.75	$ 0.72
Restricted Stock [Member]
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Effect of dilutive securities, Restricted stock	454	422	424	371
Stock Options [Member]
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Effect of dilutive securities, Stock options	32	13	26	17