Investments (Mortgage Loans Modified in a Troubled Debt Restructuring) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Contracts	Mar. 31, 2013 Contracts
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	3	0
Number of Mortgage Loans	27	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	$ 6	$ 0
Carrying Value after Specific Valuation Allowance, Post-Modification	5	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	24	0
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0
Number of Mortgage Loans	0	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	0	0
Carrying Value after Specific Valuation Allowance, Post-Modification	0	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	0
Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2	0
Number of Mortgage Loans	0	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	0	0
Carrying Value after Specific Valuation Allowance, Post-Modification	0	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	24	0
Residential [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	1	0
Number of Mortgage Loans	27	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	6	0
Carrying Value after Specific Valuation Allowance, Post-Modification	5	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 0