Investments (Valuation Allowance Rollforward by Portfolio Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	$ 34	$ 42	$ 35	$ 61
Provision/(release)	0	(1)	(1)	(20)
Ending Balance	34	41	34	41
Commercial mortgage loans portfolio segment [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	30	39	32	58
Provision/(release)	0	(1)	(2)	(20)
Ending Balance	30	38	30	38
Agricultural [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	4	3	3	3
Provision/(release)	0	0	1	0
Ending Balance	$ 4	$ 3	$ 4	$ 3