Goodwill (details) - Other Intangible Assets (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 1,126	$ 1,126
Intangible assets subject to amortization, accumulated amortization	909	840
Intangible assets subject to amortization, net	217	286
Amortization expense for other intangible assets	69	86	100
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	935	935
Intangible assets subject to amortization, accumulated amortization	830	783
Intangible assets subject to amortization, net	105	152
Amortization expense for other intangible assets	47	61	72
Fair value adjustment on claims and claim adjustment expense reserves and reinsurance recoverables [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	191	191
Intangible assets subject to amortization, accumulated amortization	79	57
Intangible assets subject to amortization, net	112	134
Amortization expense for other intangible assets	$ 22	$ 25	$ 28