Investments (Mortgage Loans Modified in a Troubled Debt Restructuring) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Contracts	Jun. 30, 2013 Contracts	Jun. 30, 2014 Contracts	Jun. 30, 2013 Contracts
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2	0	4	0
Number of Mortgage Loans	18	7	45	7
Carrying Value after Specific Valuation Allowance, Pre-Modification	$ 4	$ 5	$ 10	$ 5
Carrying Value after Specific Valuation Allowance, Post-Modification	3	5	8	5
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	0	24	0
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	0	0
Number of Mortgage Loans	0	0	0	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	0	0	0	0
Carrying Value after Specific Valuation Allowance, Post-Modification	0	0	0	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	0	0	0
Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	2	0
Number of Mortgage Loans	1	1	1	1
Carrying Value after Specific Valuation Allowance, Pre-Modification	1	4	1	4
Carrying Value after Specific Valuation Allowance, Post-Modification	1	4	1	4
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	0	24	0
Residential [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2	0	2	0
Number of Mortgage Loans	17	6	44	6
Carrying Value after Specific Valuation Allowance, Pre-Modification	3	1	9	1
Carrying Value after Specific Valuation Allowance, Post-Modification	2	1	7	1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 0	$ 0	$ 0