Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
US Treasury and Government [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	$ 20		$ 20
Purchases and issuances
Financial assets, Ending Balance	20		20
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	54	72	58	83
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	1	(1)	1
Purchases and issuances	10	9	10	19
Sales and Settlements
Transfer into Level 3		5		5
Transfer out of Level 3	0	(1)	(4)	(22)
Financial assets, Ending Balance	63	86	63	86
Residential Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	354	314	371	361
Total realized/unrealized gains (losses) included in Net income	2	1	4	2
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(7)		(1)
Purchases and issuances	0	63	6	71
Sales and Settlements	(17)	(7)	(29)	(17)
Transfer into Level 3	9	21	25	81
Transfer out of Level 3	(12)	(72)	(47)	(178)
Financial assets, Ending Balance	329	320	329	320
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	30	20	22	19
Total realized/unrealized gains (losses) included in Net income	(2)		(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0		1
Purchases and issuances
Transfer into Level 3			7
Financial assets, Ending Balance	28	20	28	20
Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	245	239	253	220
Total realized/unrealized gains (losses) included in Net income	2	4	3	5
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(2)	0	(2)	5
Purchases and issuances	0	10	12	18
Sales and Settlements	(39)	(9)	(45)	(14)
Transfer into Level 3		3		13
Transfer out of Level 3	(26)	(7)	(41)	(7)
Financial assets, Ending Balance	180	240	180	240
All other corporate [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	244	276	236	299
Total realized/unrealized gains (losses) included in Net income		1		2
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(10)	8	(10)	6
Purchases and issuances	44	41	55	59
Sales and Settlements	(4)	(13)	(6)	(24)
Transfer into Level 3	25	4	24	15
Transfer out of Level 3	(4)	0	(4)	(40)
Financial assets, Ending Balance	295	317	295	317
Trading fixed maturities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance		1		1
Transfer out of Level 3
Financial assets, Ending Balance		1		1
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	49	24	37	11
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)		2
Purchases and issuances	39	17	48	26
Sales and Settlements
Transfer into Level 3		0		4
Transfer out of Level 3	(9)		(9)
Financial assets, Ending Balance	78	41	78	41
Assets of Managed Investment Entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	30	64	40	44
Total realized/unrealized gains (losses) included in Net income	1		(3)
Purchases and issuances	6	1	6	13
Sales and Settlements	(6)	(9)	(6)	(12)
Transfer into Level 3		0		14
Transfer out of Level 3	0	(2)	(6)	(5)
Financial assets, Ending Balance	$ 31	$ 54	$ 31	$ 54