Goodwill (details) - Other Intangible Assets (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 646	$ 1,126
Intangible assets subject to amortization, accumulated amortization	481	909
Intangible assets subject to amortization, net	165	217
Amortization expense for other intangible assets	52	69	86
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	455	935
Intangible assets subject to amortization, accumulated amortization	383	830
Intangible assets subject to amortization, net	72	105
Amortization expense for other intangible assets	33	47	61
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	98	79
Intangible assets subject to amortization, net	93	112
Amortization expense for other intangible assets	$ 19	$ 22	$ 25