Investments (Valuation Allowance Rollforward by Portfolio Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	$ 294	$ 302	$ 322	$ 347
Provision (release)	15	24	12	(11)
Charge-offs, net of recoveries	(2)	0	(27)	(10)
Ending Balance	307	326	307	326
Commercial mortgage loans portfolio segment [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	230	242	258	293
Provision (release)	(4)	17	(8)	(34)
Charge-offs, net of recoveries	1	0	(23)	0
Ending Balance	227	259	227	259
Agricultural [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	42	49	44	52
Provision (release)	(3)	1	(5)	8
Charge-offs, net of recoveries	(1)	0	(1)	(10)
Ending Balance	38	50	38	50
Residential [Member]
Mortgage Loans on Real Estate [Line Items]
Beginning Balance	22	11	20	2
Provision (release)	22	6	25	15
Charge-offs, net of recoveries	(2)	0	(3)	0
Ending Balance	$ 42	$ 17	$ 42	$ 17