Income Taxes (Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Total gross deferred tax assets	$ 1,700
Non Variable Interest Entities [Member]
Unearned premium revenue	174	61
Loss and loss adjustment expense reserves	31	493
Deferral of cancellation of indebtedness income	119	119
Deferred acquisition costs	123	144
Investments in VIEs	154	173
Other		216
Total gross deferred tax liabilities	601	1,206
Compensation and employee benefits	40	40
Net operating loss and tax credit carryforwards	330	274
Capital loss carryforwards and other-than- temporary impairments	236	376
Net unrealized losses on insured derivatives	1,614	1,442
Net losses on financial instruments at fair value and foreign exchange	58	41
Net unrealized losses in accumulated other comprehensive income	105	229
Alternative minimum tax credit carryforward	22	45
Net deferred taxes on VIEs	73	43
Other (includes adjustment to deferred taxes for VIEs)	104
Total gross deferred tax assets	2,582	2,490
Valuation allowance	236	376
Net deferred tax asset	$ 1,745	$ 908