Income Taxes (Deferred Tax Assets And Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Net deferred tax asset	$ 1,200
Non Variable Interest Entities [Member]
Unearned premium revenue	241	174
Loss and loss adjustment expense reserves		31
Deferral of cancellation of indebtedness income	114	119
Deferred acquisition costs	102	123
Investments in VIEs		154
Net unrealized gains in accumulated other comprehensive income	32
Other	64
Total gross deferred tax liabilities	553	601
Compensation and employee benefits	23	40
Loss and loss adjustment expense reserves	112
Net operating loss and tax credit carryforwards	441	330
Capital loss carryforward and other-than-temporary impairments	183	236
Net unrealized losses on insured derivatives	982	1,614
Net losses on financial instruments at fair value and foreign exchange	98	58
Net unrealized losses in accumulated other comprehensive income		105
Alternative minimum tax credit carryforward	19	22
Net deferred taxes on VIEs	40	73
Other		104
Total gross deferred tax assets	1,898	2,582
Valuation allowance	146	236
Net deferred tax asset	$ 1,199	$ 1,745