Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net gains (losses) on financial instruments at fair value and foreign exchange	$ (20)	$ 24	$ 31	$ (39)
Income (loss) before income taxes	(61)	(106)	(167)	(439)
Net income (loss)	(61)	(106)	(167)	(439)
Amounts reclassified from AOCI [Member]
Net income (loss)	(1)	4	(16)	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	3	5	8	8
Income (loss) before income taxes	3	5	8	8
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)	$ (1)	$ (24)	$ (3)