Investments (Unconsolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Carrying Amount Asset	$ 13,331	$ 13,217
Carrying Amount Liability	14,527	14,176
Other limited partnership interests
Variable Interest Entity [Line Items]
Carrying Amount Asset	1,541	1,509
Carrying Amount Liability	2,729	2,460
Other investments
Variable Interest Entity [Line Items]
Carrying Amount Asset	83	71
Carrying Amount Liability	91	79
Structured Securities
Variable Interest Entity [Line Items]
Carrying Amount Asset	11,284	11,136
Carrying Amount Liability	11,284	11,136
U.S. and foreign corporate
Variable Interest Entity [Line Items]
Carrying Amount Asset	423	501
Carrying Amount Liability	$ 423	$ 501

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.

No definition available.

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- Definition

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph a
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5728-111685

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- Definition

Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

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