Derivative Financial Instruments and Off-balance sheet Financial Instruments - CDS notional amounts by credit rating (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Credit Derivatives
Notional amount	$ 3,148	$ 2,385
Credit default contracts
Credit Derivatives
Notional amount	5	5
Fair value	0	0
Credit default contracts \| Single name
Credit Derivatives
Notional amount	5	5
Fair value	0	0
AA \| Credit default contracts
Credit Derivatives
Notional amount	0	0
AA \| Credit default contracts \| Single name
Credit Derivatives
Notional amount	0	0
A \| Credit default contracts
Credit Derivatives
Notional amount	0	0
A \| Credit default contracts \| Single name
Credit Derivatives
Notional amount	0	0
BBB \| Credit default contracts
Credit Derivatives
Notional amount	0	0
BBB \| Credit default contracts \| Single name
Credit Derivatives
Notional amount	0	0
BB and lower \| Credit default contracts
Credit Derivatives
Notional amount	5	5
BB and lower \| Credit default contracts \| Single name
Credit Derivatives
Notional amount	$ 5	$ 5

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No definition available.

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- Definition

Fair value of credit risk derivative asset after deduction of credit risk derivative liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5708775-113959

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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