Earnings Per Common Share - Calculation of Both Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except 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	$ 29,520	$ 33,922	$ 63,355	$ 65,232
Basic weighted average number of common shares outstanding	200,472,592	199,244,243	200,301,438	199,085,501
Diluted weighted average number of common shares outstanding	200,472,592	199,244,243	200,301,438	199,085,501
Earnings per common share:
Basic	$ 0.15	$ 0.17	$ 0.32	$ 0.33
Diluted	$ 0.15	$ 0.17	$ 0.32	$ 0.33