Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net gains (losses) on financial instruments at fair value and foreign exchange	$ (61)	$ 14	$ (44)	$ (55)
Income (loss) before income taxes	(210)	(55)	(330)	(156)
Provision (benefit) for income taxes	1,019	(28)	971	(51)
Net income (loss)	(1,229)	(27)	(1,301)	(105)
Amounts reclassified from AOCI [Member]
Net income (loss)	4	(8)	4	(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	4	(12)	6	(4)
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	0	0	(2)	0
Net investment income	(1)	(1)	(1)	(4)
Income (loss) before income taxes	3	(13)	3	(8)
Provision (benefit) for income taxes	$ (1)	$ (5)	$ (1)	$ (3)