Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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Value of input used to measure investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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.

+ References

No definition available.

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Mortgage-Backed Securities - Significant Credit Quality Indicators (Details)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Investment Holdings [Line Items]
Amortized Cost	$ 3,303,310,000	$ 10,999,354,000
Non-Agency RMBS - Senior
Investment Holdings [Line Items]
Amortized Cost	$ 46,500,000
Non-Agency RMBS - Senior \| Credit Quality Indicator, Updated Quarterly \| Weighted Average Borrowing Rates \| Discount Rate
Investment Holdings [Line Items]
Significant Inputs	0.092
Non-Agency RMBS - Senior \| Credit Quality Indicator, Updated Quarterly \| Weighted Average Borrowing Rates \| CDR
Investment Holdings [Line Items]
Significant Inputs	0.035
Non-Agency RMBS - Senior \| Credit Quality Indicator, Updated Quarterly \| Weighted Average Borrowing Rates \| Loss Severity
Investment Holdings [Line Items]
Significant Inputs	0.583