Mortgage-Backed Securities - Collateral Characteristics (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	$ 5,696,623	$ 8,261,615
Non-Agency RMBS - Senior
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	1,109,831	1,153,458
Non-Agency RMBS - Subordinated
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	594,038	611,206
Non-Agency RMBS - Senior interest-only
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	2,983,593	3,114,930
Agency RMBS - Interest-only
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	401,285	409,940
Agency MBS - Commercial
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	123,579	302,685
Agency CMBS - Interest-only
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	$ 484,297	2,669,396
Residential Mortgage-Backed Securities | Non-Agency RMBS - Senior
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)		$ 1,153,458
Weighted Average Amortized Cost Basis (in dollars per share)	$ 45.80	$ 46.09
Weighted Average Fair Value (in dollars per share)	$ 64.66	$ 66.05
Weighted Average Coupon	5.50%	5.30%
Weighted Average Yield at Period-End	16.50%	16.40%
Residential Mortgage-Backed Securities | Non-Agency RMBS - Subordinated
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)		$ 611,206
Weighted Average Amortized Cost Basis (in dollars per share)	$ 50.00	$ 49.79
Weighted Average Fair Value (in dollars per share)	$ 47.04	$ 46.94
Weighted Average Coupon	3.80%	3.10%
Weighted Average Yield at Period-End	6.60%	6.80%
Residential Mortgage-Backed Securities | Non-Agency RMBS - Senior interest-only
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)	$ 2,983,593	$ 3,114,930
Weighted Average Amortized Cost Basis (in dollars per share)	$ 5.37	$ 5.14
Weighted Average Fair Value (in dollars per share)	$ 3.19	$ 3.17
Weighted Average Coupon	0.50%	0.70%
Weighted Average Yield at Period-End	6.90%	5.30%
Residential Mortgage-Backed Securities | Agency RMBS - Interest-only
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)		$ 409,940
Weighted Average Amortized Cost Basis (in dollars per share)	$ 4.72	$ 4.58
Weighted Average Fair Value (in dollars per share)	$ 3.22	$ 3.70
Weighted Average Coupon	0.10%	0.90%
Weighted Average Yield at Period-End	6.80%	5.00%
Commercial Mortgage Backed Securities | Agency MBS - Commercial
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)		$ 302,685
Weighted Average Amortized Cost Basis (in dollars per share)	$ 101.51	$ 101.85
Weighted Average Fair Value (in dollars per share)	$ 92.42	$ 95.62
Weighted Average Coupon	4.10%	4.30%
Weighted Average Yield at Period-End	4.00%	4.10%
Commercial Mortgage Backed Securities | Agency CMBS - Interest-only
Debt Securities, Available-for-sale [Line Items]
Principal or Notional Value at Period-End (dollars in thousands)		$ 2,669,396
Weighted Average Amortized Cost Basis (in dollars per share)	$ 1.77	$ 5.23
Weighted Average Fair Value (in dollars per share)	$ 1.90	$ 4.73
Weighted Average Coupon	0.60%	0.70%
Weighted Average Yield at Period-End	7.90%	3.40%