Investments (Mortgage Loans and Valuation Allowance by Portfolio Segment) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	$ 617	$ 622
Evaluated collectively for credit losses	55,356	55,467
Total mortgage loans	55,973	56,089
Specific credit losses	65	66
Non-specifically identified credit losses	261	256
Valuation allowances	326	322	332	347
Mortgage loan, net of valuation allowance	55,647	55,767
Commercial mortgage loans portfolio segment [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	508	506
Evaluated collectively for credit losses	39,890	40,420
Total mortgage loans	40,398	40,926
Specific credit losses	60	58
Non-specifically identified credit losses	199	200
Valuation allowances	259	258	275	293
Mortgage loan, net of valuation allowance	40,139	40,668
Agricultural [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	100	100
Evaluated collectively for credit losses	12,184	12,291
Total mortgage loans	12,284	12,391
Specific credit losses	5	7
Non-specifically identified credit losses	37	37
Valuation allowances	42	44	54	52
Mortgage loan, net of valuation allowance	12,242	12,347
Residential [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	9	16
Evaluated collectively for credit losses	3,282	2,756
Total mortgage loans	3,291	2,772
Specific credit losses	0	1
Non-specifically identified credit losses	25	19
Valuation allowances	25	20	3	2
Mortgage loan, net of valuation allowance	$ 3,266	$ 2,752