Reinsurance - Effects of Reinsurance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Premiums Earned, Net [Abstract]
Direct	$ 27,215us-gaap_DirectPremiumsEarned	$ 25,541us-gaap_DirectPremiumsEarned	$ 23,014us-gaap_DirectPremiumsEarned
Assumed	602us-gaap_AssumedPremiumsEarned	577us-gaap_AssumedPremiumsEarned	471us-gaap_AssumedPremiumsEarned
Ceded	(603)us-gaap_CededPremiumsEarned	(543)us-gaap_CededPremiumsEarned	(468)us-gaap_CededPremiumsEarned
Net	27,214us-gaap_PremiumsEarnedNet	25,575us-gaap_PremiumsEarnedNet	23,017us-gaap_PremiumsEarnedNet
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	658	317	517
Individual Life Insurance And Annuity Business Sold [Member]
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	366	335	316
Other Subsegments [Member]
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	292	(18)	201
Short Duration Contracts [Member]
Premiums Earned, Net [Abstract]
Direct	24,294	23,056	20,792
Assumed	429	394	385
Ceded	(226)	(252)	(216)
Net	24,497	23,198	20,961
Premiums Written, Net [Abstract]
Direct premiums, written versus earned
Assumed premiums, written versus earned
Ceded premiums, written versus earned
Net premiums, written versus earned
Long Duration Contracts [Member]
Premiums Earned, Net [Abstract]
Direct	2,921	2,485	2,222
Assumed	173	183	86
Net	2,717	2,377	2,056
Long Duration Contracts [Member] \| Individual Life Insurance And Annuity Business Sold [Member]
Premiums Earned, Net [Abstract]
Ceded	(254)	(176)	(186)
Long Duration Contracts [Member] \| Other Subsegments [Member]
Premiums Earned, Net [Abstract]
Ceded	$ (123)	$ (115)	$ (66)

Excess (shortfall) of assumed premiums written versus assumed premiums earned.

No definition available.

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- Definition

Excess (shortfall) of ceded premiums written versus ceded premiums earned.

+ References

No definition available.

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- Definition

Excess (shortfall) of direct premiums written versus direct premiums earned.

+ References

No definition available.

+ Details

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Excess (shortfall) of net premiums written versus net premiums earned.

+ References

No definition available.

+ Details

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- Definition

Amount of earned premiums assumed from other entities.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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-Publisher FASB

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-Publisher FASB

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-Publisher SEC

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-Number 210

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- Definition

Amount of earned premiums ceded to other entities.

+ References

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- Definition

Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

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-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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

-Publisher SEC

-Name Regulation S-X (SX)

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-Section 04

-Paragraph 1

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

-Section S99

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-URI http://asc.fasb.org/extlink&oid=6588446&loc=d3e574992-122915

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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

-Publisher SEC

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-Number 210

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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- Definition

Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

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