Schedule V (details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance for reinsurance recoverables [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	$ 363	$ 523	$ 618
Valuation and qualifying accounts, deductions	18	160	95
Valuation and qualifying accounts, balance at end of period	345	363	523
Allowance for uncollectible premiums receivable from underwriting activities [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	116	130	130
Valuation and qualifying accounts, charged to costs and expenses	23	45	61
Valuation and qualifying accounts, charged to other accounts		(1)	2
Valuation and qualifying accounts, deductions	56	58	63
Valuation and qualifying accounts, balance at end of period	83	116	130
Allowance for uncollectible deductibles [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	37	49	66
Valuation and qualifying accounts, charged to costs and expenses	6	(8)	(4)
Valuation and qualifying accounts, deductions	3	4	13
Valuation and qualifying accounts, balance at end of period	$ 40	$ 37	$ 49