Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net gains (losses) on financial instruments at fair value and foreign exchange	$ 5	$ (11)	$ 18	$ (55)
Income (loss) before income taxes	(45)	(273)	(287)	(603)
Provision (benefit) for income taxes	0	(6)	2	965
Net income (loss)	(45)	(267)	(289)	(1,568)
Amounts reclassified from AOCI [Member]
Net income (loss)	0	(5)	0	(1)
Unrealized gains (losses) on AFS, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	2	0	4	6
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	(2)	(4)	(3)	(6)
Net investment income	0	(1)	(1)	(2)
Income (loss) before income taxes	0	(5)	0	(2)
Provision (benefit) for income taxes	$ 0	$ 0	$ 0	$ (1)