Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net gains (losses) on financial instruments at fair value and foreign exchange	$ 22	$ (9)
Income (loss) before income taxes	(19)	(96)
Provision (benefit) for income taxes	(2)	2
Net income (loss)	(17)	(98)
Amounts reclassified from AOCI [Member]
Net income (loss)	7	0
Unrealized gains (losses) on AFS, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	39	1
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	(28)	(1)
Income (loss) before income taxes	11	0
Instrument-specific credit risk of liabilities measured at fair value, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	(4)	0
Income (loss) before income taxes	$ (4)	$ 0