Investments (Details 32) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Allowance for Loan and Lease Losses, Provision for Loss, Net
Beginning Balance	$ 446	$ 621	$ 481	$ 664
Provision (release)	(63)	(55)	(98)	(94)
Charge-offs, net of recoveries	(16)	0	(16)	(4)
Transfers to held-for-sale	(6)		(6)
Ending Balance	361	566	361	566
Commercial mortgage loans portfolio segment [Member]
Allowance for Loan and Lease Losses, Provision for Loss, Net
Beginning Balance	368	532	398	562
Provision (release)	(68)	(63)	(98)	(93)
Charge-offs, net of recoveries	0	0	0	0
Transfers to held-for-sale	0		0
Ending Balance	300	469	300	469
Agricultural mortgage loans portfolio segment [Member]
Allowance for Loan and Lease Losses, Provision for Loss, Net
Beginning Balance	75	76	81	88
Provision (release)	0	3	(6)	(6)
Charge-offs, net of recoveries	(16)	0	(16)	(3)
Transfers to held-for-sale	0		0
Ending Balance	59	79	59	79
Residential mortgage loans portfolio segment [Member]
Allowance for Loan and Lease Losses, Provision for Loss, Net
Beginning Balance	3	13	2	14
Provision (release)	5	5	6	5
Charge-offs, net of recoveries	0	0	0	(1)
Transfers to held-for-sale	(6)		(6)
Ending Balance	$ 2	$ 18	$ 2	$ 18