Contracts Accounted for as Credit Derivatives - Collateral Posting Requirements (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Credit Derivatives
Collateral agreed to be posted	$ 18	$ 116
Collateral Debt Obligations, Credit Derivative Contracts, Gross Par with Collateral Posting Requirements [Member]
Credit Derivatives
Amount of par subject to collateral for which the amount of collateral is capped	497	690
Collateral Debt Obligations, Maximum Posting Requirement [Member]
Credit Derivatives
Amount of par subject to collateral for which the amount of collateral is capped	464	674
Collateral Debt Obligations, Collateral Posted [Member]
Credit Derivatives
Collateral agreed to be posted	$ 18	$ 116

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

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

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624258-113959

+ 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.

+ Details

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- Details

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- Details

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- Details

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