Income Taxes (Components Of Deferred Tax Assets and Liabilities) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax liabilities [Abstract]
Unearned premium reserve	$ 143	$ 159
Deferral of cancellation of indebtedness income	46	68
Deferred acquisition costs	42	56
Net gains on financial instruments at fair value and foreign exchange	4	0
Partnership basis difference	36	30
Basis difference in foreign subsidiaries	64	40
Other	23	86
Total gross deferred tax liabilities	358	439
Deferred tax assets [Abstract]
Compensation and employee benefits	19	19
Accrued interest	177	137
Loss and loss adjustment expense reserves	142	119
Net operating loss	929	963
Foreign tax credit	7	9
Net unrealized losses on insured derivatives	29	35
Net losses on financial instruments at fair value and foreign exchange	0	45
Net unrealized losses in accumulated other comprehensive income	6	15
Alternative minimum tax credit carryforward	26	22
Net deferred taxes on VIEs	0	14
Total gross deferred tax assets	1,335	1,378
Valuation allowance	7	0
Net deferred tax asset	$ 970	$ 939