Investments (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Investment Text Details [Abstract]
Fixed maturities pledged as collateral to brokers as required under certain futures contracts	$ 54,000,000	$ 79,000,000
Investments supporting run-off settlement annuity business	3,100,000,000	3,000,000,000
Gross unrealized appreciation of investments supporting run-off settlement annuity business	883,000,000	851,000,000
Gross unrealized depreciation of investments supporting run-off settlement annuity business	8,000,000	25,000,000
Commitments to purchase fixed maturities bearing interest at a fixed market rate	58,000,000
Carrying Value Of Non Income Producing Real Estate Investments	49,000,000	49,000,000
Commercial Mortgage Loans Commitments To Extend Credit	6,000,000
Real Estate Investments Commitments To Contribute Additional Equity	7,000,000
Carrying Value Of Non Income Producing Real Estate Entities And Securities Partnerships	199,000,000	171,000,000
Commitments to contribute to limited liability entities that hold real estate or loans to real estate	197,000,000
Commitments to contribute to entities that hold seucrities diversified by issuer and maturity date	312,000,000
Percentage of the committed amounts to be disbursed by the end of next year	50.00%
Corporate Securities Included In Short Term Investments	1,100,000,000	4,100,000,000
Federal Government Securities Included In Short Term Investments	167,000,000	164,000,000
Money Market Funds Included In Short Term Investments	217,000,000	40,000,000
Trading and hybrid securities excluded from gross unrealized appreciation	16,000,000	30,000,000
Financing Receivables Credit Quality Text Details [Abstract]
Financing Receivable Credit Quality Debt Service Coverage	1.56	1.40
Financing Receivable Credit Quality Loan To Value Ratio	65.00%	70.00%
Problem And Potential Problem Mortgage Loans	215,000,000	336,000,000
Increase To Commercial Mortgage Loan Valuation Reserve Pre Tax	10,000,000
Increase To Commercial Mortgage Loan Valuation Reserve After Tax	7,000,000
Commercial Mortage Loans With Increased Valuation Reserves Industrial Number	3
Commercial Mortage Loans With Increased Valuation Reserves Retail Number	1
Average Recorded Investment Impaired Commercial Mortgage Loans	167,000,000	176,000,000
Mortgage Loans Restructured	119,000,000	65,000,000
Modified Loans Note 1	100,000,000	55,000,000
Modified Loans Note 2	19,000,000	10,000,000
Paydown Of Modified Loan Note 1	46,000,000
Remaining Amount Of Modified Loan Note 1 Reclassified To Good Standing	54,000,000
Included in fixed maturities:
Trading securities in fixed maturities	1,000,000	2,000,000
Hybrid Securities Included In Fixed Maturities	15,000,000	28,000,000
Total	16,000,000	30,000,000
Included in equity securities:
Hybrid securities in equity securities	70,000,000	65,000,000
Amortized Cost:
Due in one year or less	1,121,000,000
Due after one year through five years	5,211,000,000
Due after five years through ten years	5,283,000,000
Due after ten years	2,850,000,000
Mortgage and other asset-backed securities	1,000,000,000
Total	15,465,000,000
Fair Value:
Due in one year or less	1,141,000,000
Due after one year through five years	5,633,000,000
Due after five years through ten years	5,973,000,000
Due after ten years	3,796,000,000
Mortgage and other asset-backed securities	1,146,000,000
Total	17,689,000,000
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	2,851,000,000	3,301,000,000
Other Long Term Investments [Line Items]
Other long-term investments	1,255,000,000	1,058,000,000
Schedule Of Financing Receivable Allowance For Credit Losses [Abstract]
Reserve balance, January 1,	19,000,000	12,000,000
Increase in valuation reserves	10,000,000	16,000,000
Charge-offs upon sales and repayments, net of recoveries	(3,000,000)	(1,000,000)
Transfers to foreclosed real estate	(3,000,000)	(8,000,000)
Transfers to other long-term investments	(16,000,000)	0
Reserve balance, December 31,	7,000,000	19,000,000
Real Estate Entities [Member]
Other Long Term Investments [Line Items]
Other long-term investments	823,000,000	665,000,000
Security Partnerships [Member]
Other Long Term Investments [Line Items]
Other long-term investments	343,000,000	298,000,000
Interest Rate And Foreign Currency Swaps [Member]
Other Long Term Investments [Line Items]
Other long-term investments	6,000,000	12,000,000
Mezzanine Loans [Member]
Other Long Term Investments [Line Items]
Other long-term investments	31,000,000	31,000,000
Other Long Term Investments [Member]
Other Long Term Investments [Line Items]
Other long-term investments	52,000,000	52,000,000
One Year From Balance Sheet Date [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	419,000,000
More than One and within Two Years from Balance Sheet Date [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	290,000,000
More Than Two And Within Three Years From Balance Sheet Date [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	318,000,000
More Than Three And Within Four Years From Balance Sheet Date [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	791,000,000
More than Four Years from Balance Sheet Date and Thereafter [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	1,033,000,000
Pacific Region [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	966,000,000	893,000,000
South Atlantic Region [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	730,000,000	870,000,000
New England Region [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	387,000,000	450,000,000
Central Region [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	352,000,000	511,000,000
Middle Atlantic [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	300,000,000	391,000,000
Mountain [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	116,000,000	186,000,000
Office Buildings [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	866,000,000	1,014,000,000
Apartment Building [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	571,000,000	705,000,000
Industrial [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	532,000,000	670,000,000
Hotels [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	463,000,000	542,000,000
Retail Facilities [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	346,000,000	297,000,000
Other Property [Member]
Mortgage Loans On Real Estate Commercia Land Consumernet Investment Based Operations Presentation [Line Items]
Commercial mortgage loans and real estate investments	73,000,000	73,000,000
Portion At Amortized Cost Disclosure [Member]
Included in fixed maturities:
Trading securities in fixed maturities	1,000,000	2,000,000
Hybrid Securities Included In Fixed Maturities	15,000,000	26,000,000
Included in equity securities:
Hybrid securities in equity securities	$ 84,000,000	$ 90,000,000