Consolidated Balance Sheets (Parenthetical) Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Mortgage-backed securities (including pledged of $2,467,859 and $5,024,625, respectively), at fair value	$ 2,467,859	$ 5,024,625
Mortgage loans held for investment (includes $6,264 and $8,857 at fair value, respectively); see Note 3	$ 6,264	$ 8,857
Preferred Stock, Shares Authorized	50,000,000	50,000,000
Preferred Stock, Shares Outstanding	7,248,330	6,788,330
Preferred Stock, Shares Issued	7,248,330	6,788,330
Preferred Stock, Liquidation Preference, Value	$ 181,208	$ 169,708
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	90,000,000	90,000,000
Common Stock, Shares, Issued	23,697,970	22,945,993
Common Stock, Shares, Outstanding	23,697,970	22,945,993
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01