Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Agency securities, pledged securities	$ 4,706,610	$ 11,188,502
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares outstanding (in shares)		8,383,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	125,000,000	125,000,000
Common stock, shares issued (in shares)	64,730,000	58,877,000
Common stock, shares outstanding (in shares)	64,730,000	58,877,000
7.875% Series B
Preferred stock, par value (in dollars per share)		$ 0.001
Preferred stock, dividend rate	7.875%	7.875%
Preferred stock, shares issued (in shares)		8,383,000
Preferred stock, shares outstanding (in shares)		8,383,000
Preferred stock, aggregate liquidation preference		$ 209,583
7.000% Series C
Preferred stock, dividend rate	7.00%
Preferred stock, shares issued (in shares)	5,303,000
Preferred stock, shares outstanding (in shares)	5,303,000
Preferred stock, aggregate liquidation preference	$ 132,588
Credit Risk and Non-Agency Securities
Trading securities pledged		$ 810,549