Derivative Financial Instruments (Details 5) $ in Millions	6 Months Ended
Jun. 30, 2017 USD ($) entity	Dec. 31, 2016 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Term of credit default swaps (in years)	5 years
Credit Derivatives
Notional amount	$ 4,374	$ 3,776
The number of reference entities generally included in a CDX index \| entity	125
Credit default contracts
Credit Derivatives
Notional amount	$ 210	245
Fair value	1	(1)
Credit default contracts \| Single name \| Corporate debt
Credit Derivatives
Notional amount	30	65
Fair value	0	1
Credit default contracts \| First-to-default Basket \| Municipal
Credit Derivatives
Notional amount	100	100
Fair value	0	(3)
Credit default contracts \| Index \| Corporate debt
Credit Derivatives
Notional amount	80	80
Fair value	1	1
AA \| Credit default contracts
Credit Derivatives
Notional amount	1	21
AA \| Credit default contracts \| Single name \| Corporate debt
Credit Derivatives
Notional amount	0	20
AA \| Credit default contracts \| First-to-default Basket \| Municipal
Credit Derivatives
Notional amount	0	0
AA \| Credit default contracts \| Index \| Corporate debt
Credit Derivatives
Notional amount	1	1
A \| Credit default contracts
Credit Derivatives
Notional amount	17	29
A \| Credit default contracts \| Single name \| Corporate debt
Credit Derivatives
Notional amount	0	10
A \| Credit default contracts \| First-to-default Basket \| Municipal
Credit Derivatives
Notional amount	0	0
A \| Credit default contracts \| Index \| Corporate debt
Credit Derivatives
Notional amount	17	19
BBB \| Credit default contracts
Credit Derivatives
Notional amount	174	185
BBB \| Credit default contracts \| Single name \| Corporate debt
Credit Derivatives
Notional amount	25	35
BBB \| Credit default contracts \| First-to-default Basket \| Municipal
Credit Derivatives
Notional amount	100	100
BBB \| Credit default contracts \| Index \| Corporate debt
Credit Derivatives
Notional amount	49	50
BB and lower \| Credit default contracts
Credit Derivatives
Notional amount	18	10
BB and lower \| Credit default contracts \| Single name \| Corporate debt
Credit Derivatives
Notional amount	5	0
BB and lower \| Credit default contracts \| First-to-default Basket \| Municipal
Credit Derivatives
Notional amount	0	0
BB and lower \| Credit default contracts \| Index \| Corporate debt
Credit Derivatives
Notional amount	$ 13	$ 10

The general number of entities included in a credit derivative index group.

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

Term of the credit risk derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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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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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5708775-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

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- References

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