Employee Benefit Plans (Significant Unobservable Inputs) (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	$ 9,003	$ 8,024
Purchases, sales, issuances and settlements, net	(3)	(10)
Estimated fair value of plan assets at December 31,	8,751	9,003
Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	2,784
Estimated fair value of plan assets at December 31,	3,057	2,784
Foreign government
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	825
Estimated fair value of plan assets at December 31,	781	825
Other (1)
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	196
Estimated fair value of plan assets at December 31,	361	196
Common stock - domestic
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	951
Estimated fair value of plan assets at December 31,	775	951
Other investments
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	803
Estimated fair value of plan assets at December 31,	839	803
Derivative assets
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	91
Estimated fair value of plan assets at December 31,	105	91
Level 3
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	923
Estimated fair value of plan assets at December 31,	901	923
Level 3 \| Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	80	59
Realized gains (losses)	1	3
Unrealized gains (losses)	(4)	0
Purchases, sales, issuances and settlements, net	8	11
Transfers into and/or out of Level 3	(7)	7
Estimated fair value of plan assets at December 31,	78	80
Level 3 \| Foreign government
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	17	11
Realized gains (losses)	0	0
Unrealized gains (losses)	(1)	0
Purchases, sales, issuances and settlements, net	2	6
Transfers into and/or out of Level 3	(1)	0
Estimated fair value of plan assets at December 31,	17	17
Level 3 \| Other (1)
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	8	19
Realized gains (losses)	0	0
Unrealized gains (losses)	2	0
Purchases, sales, issuances and settlements, net	(1)	(2)
Transfers into and/or out of Level 3	(2)	(9)
Estimated fair value of plan assets at December 31,	7	8
Level 3 \| Common stock - domestic
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	0	148
Realized gains (losses)	0	0
Unrealized gains (losses)	0	0
Purchases, sales, issuances and settlements, net	0	0
Transfers into and/or out of Level 3	0	(148)
Estimated fair value of plan assets at December 31,	0	0
Level 3 \| Other investments
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	745	602
Realized gains (losses)	0	(13)
Unrealized gains (losses)	55	112
Purchases, sales, issuances and settlements, net	(77)	(104)
Transfers into and/or out of Level 3	0	148
Estimated fair value of plan assets at December 31,	723	745
Level 3 \| Derivative assets
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Estimated fair value of plan assets at January 1,	73	37
Realized gains (losses)	(11)	(16)
Unrealized gains (losses)	(9)	18
Purchases, sales, issuances and settlements, net	23	34
Transfers into and/or out of Level 3	0	0
Estimated fair value of plan assets at December 31,	$ 76	$ 73

Actual return on plan assets, separately identifying the amount related to assets sold during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920

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- Definition

Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 35
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=49178875&loc=d3e12355-114930

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

Amount of increase (decrease) in plan assets from purchases, sales and settlement of plan obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)(B)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(iv)(02)(B)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920

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- Definition

Transfers in and out of Level 3. For example, transfers due to changes in the observability of significant inputs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)(C)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(iv)(02)(C)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920

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