Goodwill (details) - Other Intangible Assets (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 646		$ 646		$ 646
Intangible assets subject to amortization, accumulated amortization	504		504		481
Intangible assets subject to amortization, net	142		142		165
Amortization expense for other intangible assets	12	12	23	28
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	455		455		455
Intangible assets subject to amortization, accumulated amortization	398		398		383
Intangible assets subject to amortization, net	57		57		72
Amortization expense for other intangible assets	8	7	15	18
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		191
Intangible assets subject to amortization, accumulated amortization	106		106		98
Intangible assets subject to amortization, net	85		85		93
Amortization expense for other intangible assets	$ 4	$ 5	$ 8	$ 10