Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended			6 Months Ended
	Jun. 30, 2012 Liabilities of Managed Investment Entities [Member]	Jun. 30, 2011 Liabilities of Managed Investment Entities [Member]	Jun. 30, 2012 Liabilities of Managed Investment Entities [Member]	Jun. 30, 2011 Liabilities of Managed Investment Entities [Member]	Jun. 30, 2012 Embedded derivatives [Member]	Jun. 30, 2011 Embedded derivatives [Member]	Jun. 30, 2012 Embedded derivatives [Member]	Jun. 30, 2011 Embedded derivatives [Member]	Jun. 30, 2012 States, municipalities and political subdivisions [Member]	Jun. 30, 2011 States, municipalities and political subdivisions [Member]	Jun. 30, 2012 States, municipalities and political subdivisions [Member]	Jun. 30, 2011 States, municipalities and political subdivisions [Member]	Jun. 30, 2012 Residential Mortgage Backed Securities [Member]	Jun. 30, 2011 Residential Mortgage Backed Securities [Member]	Jun. 30, 2012 Residential Mortgage Backed Securities [Member]	Jun. 30, 2011 Residential Mortgage Backed Securities [Member]	Jun. 30, 2011 Commercial Mortgage Backed Securities [Member]	Jun. 30, 2012 Commercial Mortgage Backed Securities [Member]	Jun. 30, 2011 Commercial Mortgage Backed Securities [Member]	Mar. 31, 2012 Commercial Mortgage Backed Securities [Member]	Jun. 30, 2012 Assets of Managed Investment Entities [Member]	Jun. 30, 2011 Assets of Managed Investment Entities [Member]	Jun. 30, 2012 Assets of Managed Investment Entities [Member]	Jun. 30, 2011 Assets of Managed Investment Entities [Member]	Jun. 30, 2012 All other corporate [Member]	Jun. 30, 2011 All other corporate [Member]	Jun. 30, 2012 All other corporate [Member]	Jun. 30, 2011 All other corporate [Member]	Jun. 30, 2012 Equity securities [Member]	Jun. 30, 2012 Equity securities [Member]	Jun. 30, 2011 Equity securities [Member]	Mar. 31, 2011 Equity securities [Member]	Jun. 30, 2011 Trading fixed maturities [Member]	Jun. 30, 2012 Trading fixed maturities [Member]	Mar. 31, 2012 Trading fixed maturities [Member]	Dec. 31, 2011 Trading fixed maturities [Member]	Mar. 31, 2011 Trading fixed maturities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance									$ 72	$ 21	$ 83	$ 20	$ 314	$ 271	$ 361	$ 312	$ 9	$ 19	$ 6	$ 20	$ 64	$ 54	$ 44	$ 48	$ 515	$ 424	$ 519	$ 436	$ 24	$ 11	$ 21	$ 21	$ 3	$ 1	$ 1	$ 1	$ 1
Total realized/unrealized gains (losses) included in Net income													1		2	1								(1)	5	1	7	(1)
Total realized/unrealized Gains (losses) included in other comprehensive income (loss)									1		1	1		(2)		(2)		1							8	6	11	6			2
Purchases and issuances									9	53	19	53	63	17	71	17					1	9	13	16	51	46	77	91	17	26
Sales and Settlements													(7)	(7)	(17)	(20)					(9)	(2)	(12)	(6)	(22)	(26)	(38)	(37)			(2)
Transfer into Level 3									5	10	5	10	21		81	7	1		4			2	14	8	7	2	28	24		4
Transfer out of Level 3									(1)		(22)		(72)	(24)	(178)	(60)					(2)	(10)	(5)	(12)	(7)	(71)	(47)	(137)					(2)
Financial assets, Ending Balance									86	84	86	84	320	255	320	255	10	20	10	20	54	53	54	53	557	382	557	382	41	41	21	21	1	1	1	1	1
Changes in balances of Level 3 financial liabilities
Financial liabilities, Beginning Balance	(2,554)	(2,316)	(2,593)	(2,258)	(483)	(234)	(395)	(190)
Total realized/unrealized gains (losses) included in Net income	(19)	(10)	(103)	(72)		(10)	(62)	(29)
Purchases and issuances			(366)
Purchases and issuances					(39)	(60)	(73)	(90)
Sales and Settlements	144	4	633	8	10	5	18	10
Financial liabilities, Ending Balance	$ (2,429)	$ (2,322)	$ (2,429)	$ (2,322)	$ (512)	$ (299)	$ (512)	$ (299)