Investments (Credit Quality Indicators For Mortgage Loans) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 7,033	$ 7,043
Percentage of total mortgage loans on real estate	100.00%	100.00%
Loan-To-Value Ratio, Less Than 65% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	5,827	5,677
Percentage of total mortgage loans on real estate	82.90%	80.60%
Debt-service coverage ratio	1.73	1.68
Loan-To-Value Ratio, 65% To 74% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	761	897
Percentage of total mortgage loans on real estate	10.80%	12.70%
Debt-service coverage ratio	1.44	1.39
Loan-To-Value Ratio, 75% To 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	396	386
Percentage of total mortgage loans on real estate	5.60%	5.50%
Debt-service coverage ratio	0.83	0.84
Loan-To-Value Ratio, Greater Than 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 49	$ 83
Percentage of total mortgage loans on real estate	0.70%	1.20%
Debt-service coverage ratio	0.76	0.66