Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Mortgage-backed securities, pledged assets	$ 13,932,415	$ 16,538,214
Mortgage loans held for investment, pledged assets	50,143	0
Pledged cash	376,081	323,791
Mortgage loans held for sale, pledged assets	$ 17,542	$ 0
Series A preferred stock dividend rate per year	7.625%	7.625%
7.625% Series A Cumulative Redeemable Preferred stock, par value	$ 0.001	$ 0.001
7.625% Series A Cumulative Redeemable Preferred stock, shares authorized	25,000,000	25,000,000
7.625% Series A Cumulative Redeemable Preferred stock, shares issued	11,500,000	11,500,000
7.625% Series A Cumulative Redeemable Preferred stock, shares outstanding	11,500,000	11,500,000
7.625% Series A Cumulative Redeemable Preferred stock, aggregate Liquidation Preference	$ 287,500	$ 287,500
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	95,773,767	96,771,158
Common stock, shares outstanding	95,773,767	96,771,158
Asset of collateralized financing entity	$ 227,444
Liabilities of collateralized financing entity	$ 57,784