Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net gains (losses) on financial instruments at fair value and foreign exchange	$ (11)	$ 38	$ (55)	$ (17)
Income (loss) before income taxes	(273)	55	(603)	(101)
Provision (benefit) for income taxes	(6)	24	965	(28)
Net income (loss)	(267)	31	(1,568)	(73)
Amounts reclassified from AOCI [Member]
Net income (loss)	(5)	0	(1)	(5)
Unrealized gains (losses) on AFS, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	0	1	6	(3)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	(4)	0	(6)	0
Net investment income	(1)	0	(2)	(4)
Income (loss) before income taxes	(5)	1	(2)	(7)
Provision (benefit) for income taxes	$ 0	$ 1	$ (1)	$ (2)