Investments (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
U.S. Government and government agencies [Member]
Available for sale securities in a continuous unrealized loss position
Fair Value - Less than twelve months	$ 27	$ 2
Fair Value as % of Cost - Less than twelve months	100.00%	100.00%
Fair Value - Twelve months or more
Fair Value as % of Cost - Twelve months or more
States, municipalities and political subdivisions [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(5)	(2)
Fair Value - Less than twelve months	250	120
Fair Value as % of Cost - Less than twelve months	98.00%	98.00%
Unrealized Loss - Twelve months or more	(1)	(1)
Fair Value - Twelve months or more	22	59
Fair Value as % of Cost - Twelve months or more	96.00%	98.00%
Foreign government [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months
Fair Value - Less than twelve months		1
Fair Value as % of Cost - Less than twelve months		100.00%
Fair Value - Twelve months or more
Fair Value as % of Cost - Twelve months or more
Residential Mortgage Backed Securities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(36)	(59)
Fair Value - Less than twelve months	846	1,141
Fair Value as % of Cost - Less than twelve months	96.00%	95.00%
Unrealized Loss - Twelve months or more	(107)	(121)
Fair Value - Twelve months or more	502	473
Fair Value as % of Cost - Twelve months or more	82.00%	80.00%
Commercial Mortgage Backed Securities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(1)	(6)
Fair Value - Less than twelve months	38	183
Fair Value as % of Cost - Less than twelve months	97.00%	97.00%
Fair Value - Twelve months or more	2	18
Fair Value as % of Cost - Twelve months or more	100.00%	100.00%
All other corporate [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(12)	(43)
Fair Value - Less than twelve months	602	940
Fair Value as % of Cost - Less than twelve months	98.00%	96.00%
Unrealized Loss - Twelve months or more	(11)	(17)
Fair Value - Twelve months or more	112	114
Fair Value as % of Cost - Twelve months or more	91.00%	87.00%
Fixed maturity securities [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(54)	(110)
Fair Value - Less than twelve months	1,763	2,387
Fair Value as % of Cost - Less than twelve months	97.00%	96.00%
Unrealized Loss - Twelve months or more	(119)	(139)
Fair Value - Twelve months or more	638	664
Fair Value as % of Cost - Twelve months or more	84.00%	83.00%
Common stocks [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months	(8)	(19)
Fair Value - Less than twelve months	70	169
Fair Value as % of Cost - Less than twelve months	90.00%	90.00%
Unrealized Loss - Twelve months or more	(1)	(1)
Fair Value - Twelve months or more	4	4
Fair Value as % of Cost - Twelve months or more	80.00%	80.00%
Perpetual preferred stocks [Member]
Available for sale securities in a continuous unrealized loss position
Unrealized Loss - Less than twelve months		(1)
Fair Value - Less than twelve months	2	23
Fair Value as % of Cost - Less than twelve months	100.00%	96.00%
Unrealized Loss - Twelve months or more	(3)	(7)
Fair Value - Twelve months or more	$ 22	$ 31
Fair Value as % of Cost - Twelve months or more	88.00%	82.00%