Investments (Variable Interest Entities - Narrative) (Details) - RMBS - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Proceeds from securitization of loan held for investment carrying value	$ 308	$ 443
Proceeds from Securitizations of Loans Held-for-investment	313	467
Gain (Loss) on Securitization of Financial Assets	5	24
Transfers of Financial Assets Accounted for as Sale, Initial Fair Value of Assets Obtained as Proceeds	$ 43	$ 131

Proceeds from securitization of loan held for investment carrying value

No definition available.

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- Definition

A gain (loss) realized on a transfer, accounted for as a sale, of all or a portion of financial assets in which the transferor surrenders control and receives consideration other than a beneficial interest in the assets transferred. Reflects the amount of sales proceeds in excess of, or deficient from, the sum of the carrying amounts of transferred financial assets plus transaction costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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-Section S99
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section S99
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-Subparagraph (SX 210.5-03(b)(9)(a))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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- Definition

The cash inflow from the securitization of loans held for investment. Securitization is the structured process whereby interests in loans and other receivables are packaged, underwritten, and sold in the form of asset-backed securities.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-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

Represents the initial fair value recorded for assets received on transfer of financial assets in a securitization, asset-backed financing arrangement, or a similar transfer which transaction is recognized as a sale of the transferred financial assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

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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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