Mortgage-Backed Securities - Gains and Losses from Sales of Investments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Investment Holdings [Line Items]
Net realized gain (loss)	$ 7,517	$ 26,380	$ 45,313	$ 102,234
Non-Agency RMBS
Investment Holdings [Line Items]
Proceeds from sales:	15,418	108,163	47,877	141,960
Gross realized gains:	11,229	20,017	37,742	21,274
Gross realized losses:	(2,503)	(6,179)	(4,955)	(6,179)
Agency RMBS
Investment Holdings [Line Items]
Proceeds from sales:	626	0	626	5,710,134
Gross realized gains:	0	0	0	74,264
Gross realized losses:	(1,209)	0	(1,209)	(5,816)
Agency CMBS
Investment Holdings [Line Items]
Proceeds from sales:	0	221,651	201,037	326,668
Gross realized gains:	0	12,542	13,735	18,691
Gross realized losses:	$ 0	$ 0	$ 0	$ 0

Net gain (loss) resulting from the sales of securitized, pay-through debt securities collateralized by real estate mortgage loans (mortgages).

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The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The difference between the carrying value and the sale price of an investment. A loss would be recognized when the sale price of the investment is less than the carrying value of the investment. This element refers to the Loss included in earnings and not to the cash proceeds of the sale.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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