Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	100,361,000	94,152,000
Common stock, shares outstanding (in shares)	100,361,000	94,152,000
Agency Securities
Pledged securities	$ 5,554,860	$ 3,995,804
U.S. Treasuries
Pledged securities	$ 1,104,970	$ 98,859
7.00% Series C
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000
Preferred stock, dividend rate	7.00%	7.00%
Preferred stock, shares issued (in shares)	6,847,000	6,847,000
Preferred stock, shares outstanding (in shares)	6,847,000	6,847,000
Preferred stock, liquidation preference (in dollars per share)	$ 25.00	$ 25.00