Schedule V (details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for reinsurance recoverables [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	$ 345	$ 363	$ 523
Valuation and qualifying accounts, deductions	87	18	160
Valuation and qualifying accounts, balance at end of period	258	345	363
Allowance for uncollectible premiums receivable from underwriting activities [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	83	116	130
Valuation and qualifying accounts, charged to costs and expenses	44	23	45
Valuation and qualifying accounts, charged to other accounts			(1)
Valuation and qualifying accounts, deductions	51	56	58
Valuation and qualifying accounts, balance at end of period	76	83	116
Allowance for uncollectible deductibles [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	40	37	49
Valuation and qualifying accounts, charged to costs and expenses	4	6	(8)
Valuation and qualifying accounts, deductions	3	3	4
Valuation and qualifying accounts, balance at end of period	$ 41	$ 40	$ 37