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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 18,773	$ 28,478	$ 45,283	$ 52,423
Basic Earnings Per Share, Weighted average common shares outstanding	103,904	100,981	101,862	101,031
Basic Earnings Per Share	$ 0.18	$ 0.28	$ 0.44	$ 0.52
Diluted Earnings Per Share, Net income	$ 18,773	$ 28,478	$ 45,283	$ 52,423
Diluted Earnings Per Share, Weighted average common shares outstanding	103,904	100,981	101,862	101,031
Effect of dilutive securities: Restricted stock	424	363	471	406
Effect of dilutive securities: Stock options	33	8	30	11
Diluted Earnings Per Share, Weighted average shares outstanding	104,361	101,352	102,363	101,448
Diluted earnings per share	$ 0.18	$ 0.28	$ 0.44	$ 0.52