Investments (Mortgage Loans and Valuation Allowance by Portfolio Segment) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	$ 622	$ 733
Evaluated collectively for credit losses	55,467	53,540
Total mortgage loans	56,089	54,273
Specific credit losses	66	117
Non-specifically identified credit losses	256	230
Valuation allowances	322	347	481	664
Mortgage loan, net of valuation allowance	55,767	53,926
Commercial mortgage loans portfolio segment [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	506	539
Evaluated collectively for credit losses	40,420	39,933
Total mortgage loans	40,926	40,472
Specific credit losses	58	94
Non-specifically identified credit losses	200	199
Valuation allowances	258	293	398	562
Mortgage loan, net of valuation allowance	40,668	40,179
Agricultural [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	100	181
Evaluated collectively for credit losses	12,291	12,662
Total mortgage loans	12,391	12,843
Specific credit losses	7	21
Non-specifically identified credit losses	37	31
Valuation allowances	44	52	81	88
Mortgage loan, net of valuation allowance	12,347	12,791
Residential [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	16	13
Evaluated collectively for credit losses	2,756	945
Total mortgage loans	2,772	958
Specific credit losses	1	2
Non-specifically identified credit losses	19	0
Valuation allowances	20	2	2	14
Mortgage loan, net of valuation allowance	$ 2,752	$ 956