Investments (Credit Quality Indicators For Mortgage Loans) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 7,130	$ 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	5,958	5,677
Percentage of total mortgage loans on real estate	83.60%	80.60%
Debt-service coverage ratio	1.79	1.68
Loan-To-Value Ratio, 65% To 74% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	723	897
Percentage of total mortgage loans on real estate	10.10%	12.70%
Debt-service coverage ratio	1.42	1.39
Loan-To-Value Ratio, 75% To 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	404	386
Percentage of total mortgage loans on real estate	5.70%	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	$ 45	$ 83
Percentage of total mortgage loans on real estate	0.60%	1.20%
Debt-service coverage ratio	0.66	0.66