Investments (Details 1) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
U.S. Government and government agencies [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	$ 0	$ 0
Fair Value - Less than twelve months	33	22
Fair Value as % of Cost - Less than twelve months	100.00%	100.00%
Unrealized Loss - Twelve months or more	0	0
Fair Value - Twelve months or more	0	0
Fair Value as % of Cost - Twelve months or more	0.00%	0.00%
States, municipalities and political subdivisions [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(99)	(5)
Fair Value - Less than twelve months	1,824	285
Fair Value as % of Cost - Less than twelve months	95.00%	98.00%
Unrealized Loss - Twelve months or more	(1)	0
Fair Value - Twelve months or more	26	24
Fair Value as % of Cost - Twelve months or more	96.00%	100.00%
Residential Mortgage Backed Securities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(9)	(3)
Fair Value - Less than twelve months	487	146
Fair Value as % of Cost - Less than twelve months	98.00%	98.00%
Unrealized Loss - Twelve months or more	(27)	(51)
Fair Value - Twelve months or more	252	411
Fair Value as % of Cost - Twelve months or more	90.00%	89.00%
Commercial Mortgage Backed Securities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(3)	0
Fair Value - Less than twelve months	73	16
Fair Value as % of Cost - Less than twelve months	96.00%	100.00%
Unrealized Loss - Twelve months or more	0	0
Fair Value - Twelve months or more	0	0
Fair Value as % of Cost - Twelve months or more	0.00%	0.00%
Asset-backed Securities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(15)	0
Fair Value - Less than twelve months	1,013	146
Fair Value as % of Cost - Less than twelve months	99.00%	100.00%
Unrealized Loss - Twelve months or more	(1)	(2)
Fair Value - Twelve months or more	28	57
Fair Value as % of Cost - Twelve months or more	97.00%	97.00%
All other corporate [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(83)	(3)
Fair Value - Less than twelve months	2,150	237
Fair Value as % of Cost - Less than twelve months	96.00%	99.00%
Unrealized Loss - Twelve months or more	(2)	(2)
Fair Value - Twelve months or more	34	51
Fair Value as % of Cost - Twelve months or more	94.00%	96.00%
Fixed maturities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(209)	(11)
Fair Value - Less than twelve months	5,580	852
Fair Value as % of Cost - Less than twelve months	96.00%	99.00%
Unrealized Loss - Twelve months or more	(31)	(55)
Fair Value - Twelve months or more	340	543
Fair Value as % of Cost - Twelve months or more	92.00%	91.00%
Common stocks [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(6)	(8)
Fair Value - Less than twelve months	98	88
Fair Value as % of Cost - Less than twelve months	94.00%	92.00%
Unrealized Loss - Twelve months or more	0	0
Fair Value - Twelve months or more	0	0
Fair Value as % of Cost - Twelve months or more	0.00%	0.00%
Perpetual preferred stocks [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(7)	0
Fair Value - Less than twelve months	84	7
Fair Value as % of Cost - Less than twelve months	92.00%	100.00%
Unrealized Loss - Twelve months or more	(3)	(1)
Fair Value - Twelve months or more	$ 23	$ 25
Fair Value as % of Cost - Twelve months or more	88.00%	96.00%