Residential Mortgage Securities and MSR Related Assets (Sales of Residential Mortgage Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	$ 3,062,858	$ 908,696	$ 538,965
Gains/(Losses)	61,697	62,002	61,307
Agency MBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	1,500,875	360,634	122,027
Gains/(Losses)	(19,291)	499	(6,810)
Non-Agency MBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	1,318,958	291,391	117,060
Gains/(Losses)	107,999	50,360	36,744
CRT securities
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	243,025	256,671	299,878
Gains/(Losses)	$ (27,011)	$ 11,143	$ 31,373

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=121586364&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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