Earnings Per Share - Schedule of Earnings Per Share, Basic (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic earnings per share:
Net income available to common stockholders	$ 34,466	$ 1,958	$ 41,464	$ 10,147
Basic weighted-average shares of common stock outstanding	171,758	140,368	167,515	138,257
Basic earnings per share	$ 0.20	$ 0.01	$ 0.25	$ 0.07