Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net gains (losses) on financial instruments at fair value and foreign exchange	$ 11	$ 13	$ 42	$ (26)
Income (loss) before income taxes	(123)	(58)	(290)	(497)
Net income (loss)	(123)	(58)	(290)	(497)
Amounts reclassified from AOCI [Member]
Net income (loss)	(9)	7	(25)	12
Unrealized gains (losses) on AFS, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	3	9	11	17
Income (loss) before income taxes	3	9	11	17
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	$ (12)	$ (2)	$ (36)	$ (5)