Goodwill (details) - Other Intangible Assets (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 646		$ 646
Intangible assets subject to amortization, accumulated amortization	492		481
Intangible assets subject to amortization, net	154		165
Amortization expense for other intangible assets	11	16
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	455		455
Intangible assets subject to amortization, accumulated amortization	390		383
Intangible assets subject to amortization, net	65		72
Amortization expense for other intangible assets	7	11
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	102		98
Intangible assets subject to amortization, net	89		93
Amortization expense for other intangible assets	$ 4	$ 5