Investment Income and Gains and Losses - Net Investment Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	$ 1,206	$ 1,200	$ 1,184
Less: investment expenses	40	36	40
Net investment income	1,166us-gaap_NetInvestmentIncome	1,164us-gaap_NetInvestmentIncome	1,144us-gaap_NetInvestmentIncome
Net investment income for separate accounts	225	232	181
Fixed Maturities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	876	823	843
Equity securities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	3	6	4
Commercial Mortgage Loans [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	133	174	192
Policy Loans [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	72	74	74
Other Long Term Investments [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	105	101	57
Short-term investments and cash [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Gross investment income	$ 17	$ 22	$ 14

Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein. Also includes the total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue.

No definition available.

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- Definition

Net investment income related to separate accounts that are not reflected in the Company's revenue for the year.

+ References

No definition available.

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- Definition

Amount of expenses related to the generation of investment income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.9)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Definition

Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 7

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