CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
MBS and GSE CRT pledged as collateral	$ 17,185,870,000	$ 17,560,811,000
Agency RMBS pledged related to unsettled sales	$ 189,263,000	$ 0
Preferred Stock - par value (in usd per share)	$ 0.01	$ 0.01
Preferred Stock - shares authorized	50,000,000	50,000,000
Common Stock - par value (in usd per share)	$ 0.01	$ 0.01
Common Stock - shares authorized	450,000,000	450,000,000
Common Stock - shares issued	111,636,723	111,624,159
Common Stock - shares outstanding	111,636,723	111,624,159
Series A Preferred Stock
Preferred Stock - dividend rate stated percentage	7.75%	7.75%
Preferred Stock - shares issued	5,600,000	5,600,000
Preferred Stock - shares outstanding	5,600,000	5,600,000
Preferred Stock - liquidation preference value	$ 140,000,000	$ 140,000,000
Series B Preferred Stock
Preferred Stock - dividend rate stated percentage	7.75%	7.75%
Preferred Stock - shares issued	6,200,000	6,200,000
Preferred Stock - shares outstanding	6,200,000	6,200,000
Preferred Stock - liquidation preference value	$ 155,000,000	$ 155,000,000
Series C Preferred Stock
Preferred Stock - dividend rate stated percentage	7.50%	7.50%
Preferred Stock - shares issued	11,500,000	11,500,000
Preferred Stock - shares outstanding	11,500,000	11,500,000
Preferred Stock - liquidation preference value	$ 287,500,000	$ 287,500,000