Investments (Mortgage Loans Modified in a Troubled Debt Restructuring) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Contracts	Dec. 31, 2012 Contracts
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	31	6
Carrying Value after Specific Valuation Allowance, Pre-Modification	$ 82	$ 239
Carrying Value after Specific Valuation Allowance, Post-Modification	82	215
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	1	1
Carrying Value after Specific Valuation Allowance, Pre-Modification	49	222
Carrying Value after Specific Valuation Allowance, Post-Modification	49	199
Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	3	5
Carrying Value after Specific Valuation Allowance, Pre-Modification	28	17
Carrying Value after Specific Valuation Allowance, Post-Modification	28	16
Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	27	0
Carrying Value after Specific Valuation Allowance, Pre-Modification	5	0
Carrying Value after Specific Valuation Allowance, Post-Modification	$ 5	$ 0