Securities, at Fair Value (Sale of MBS) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	$ 0	$ 116	$ 0	$ 3,062,858
Gains/(Losses)	0	48	0	61,697
Agency MBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	0	0	0	1,500,875
Gains/(Losses)	0	0	0	(19,291)
Non-Agency MBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	0	116	0	1,318,958
Gains/(Losses)	0	48	0	107,999
CRT securities
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	0	0	0	243,025
Gains/(Losses)	$ 0	$ 0	$ 0	$ (27,011)

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3179-108585

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- Definition

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.

+ References

No definition available.

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