Income Taxes (Components Of Deferred Tax Assets and Liabilities) (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Deferred tax liabilities [Abstract]
Unearned premium reserve	$ 140	$ 143
Deferral of cancellation of indebtedness income	34	46
Deferred acquisition costs	37	42
Net gains on financial instruments at fair value and foreign exchange	0	4
Partnership basis difference	29	36
Basis difference in foreign subsidiaries	2	64
Net deferred taxes on VIEs	14	0
Other	34	23
Total gross deferred tax liabilities	290	358
Deferred tax assets [Abstract]
Compensation and employee benefits	17	19
Accrued interest	198	177
Loss and loss adjustment expense reserves	104	142
Net operating loss	976	929
Foreign tax credit	62	7
Net unrealized losses on insured derivatives	29	29
Net losses on financial instruments at fair value and foreign exchange	23	0
Net unrealized losses in accumulated other comprehensive income	12	6
Alternative minimum tax credit carryforward	26	26
Total gross deferred tax assets	1,447	1,335
Valuation allowance	1,157	7
Net deferred tax asset	$ 0	$ 970