Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net gains (losses) on financial instruments at fair value and foreign exchange	$ 51	$ (63)
Income (loss) before income taxes	(106)	(333)
Net income (loss)	(106)	(333)
Amounts reclassified from AOCI [Member]
Net income (loss)	(15)	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	5	3
Income (loss) before income taxes	5	3
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	$ (20)	$ (2)