Investments Investments (Mortgage Loans Modified in a Troubled Debt Restructuring) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Contracts	Sep. 30, 2012 Contracts	Sep. 30, 2013 Contracts	Sep. 30, 2012 Contracts
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	8	5	15	5
Carrying Value after Specific Valuation Allowance, Pre-Modification	$ 74	$ 17	$ 79	$ 17
Carrying Value after Specific Valuation Allowance, Post-Modification	74	16	79	16
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	1	0	1	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	49	0	49	0
Carrying Value after Specific Valuation Allowance, Post-Modification	49	0	49	0
Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	2	5	3	5
Carrying Value after Specific Valuation Allowance, Pre-Modification	24	17	28	17
Carrying Value after Specific Valuation Allowance, Post-Modification	24	16	28	16
Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	5	0	11	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	1	0	2	0
Carrying Value after Specific Valuation Allowance, Post-Modification	$ 1	$ 0	$ 2	$ 0