Investments (Securities Lending - Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Amortized cost
Securities Financing Transaction [Line Items]
Securities Loaned	$ 28,043	$ 26,989
Estimated fair value
Securities Financing Transaction [Line Items]
Percentage of Estimated Fair Value of Securities Loaned Based on Collateral Obtained	102.00%
Securities Loaned	$ 29,853	$ 30,269
Reserve for Off-balance Sheet Activities [Member] \| Amortized cost
Securities Financing Transaction [Line Items]
Securities Loaned	217
Reserve for Off-balance Sheet Activities [Member] \| Estimated fair value
Securities Financing Transaction [Line Items]
Securities Loaned	$ 217

Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 405

-Section 55

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35710563&loc=d3e44140-110984

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant