Investments (Valuation Allowance Rollforward by Portfolio Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	$ 322	$ 347
Provision (release)	5	(11)
Charge-offs, net of recoveries	(1)	(4)
Ending Balance	326	332
Commercial mortgage loans portfolio segment [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	258	293
Provision (release)	1	(18)
Charge-offs, net of recoveries	0	0
Ending Balance	259	275
Agricultural [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	44	52
Provision (release)	(2)	6
Charge-offs, net of recoveries	0	(4)
Ending Balance	42	54
Residential [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	20	2
Provision (release)	6	1
Charge-offs, net of recoveries	(1)	0
Ending Balance	$ 25	$ 3