CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Mortgage-backed and credit risk transfer securities, pledged as collateral	$ 17,398,372	$ 14,422,198
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	111,616,551	111,594,595
Common Stock - shares outstanding	111,616,551	111,594,595
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	$ 140,000
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	$ 155,000
Series C Preferred Stock
Preferred Stock - dividend rate stated percentage	7.50%
Preferred Stock - shares issued	11,500,000
Preferred Stock - shares outstanding	11,500,000
Preferred Stock - liquidation preference value	$ 287,500