Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net gains (losses) on financial instruments at fair value and foreign exchange	$ 13	$ 44	$ (26)	$ 40
Income (loss) before income taxes	(58)	89	(497)	(137)
Net income (loss)	(58)	83	(497)	(145)
Amounts reclassified from AOCI [Member]
Net income (loss)	7	31	12	(6)
Unrealized gains (losses) on AFS, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	9	(7)	17	16
Net investment losses related to OTTI	0	42	0	5
Net investment income	0	(1)	0	(1)
Income (loss) before income taxes	9	34	17	20
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	$ (2)	$ (3)	$ (5)	$ (26)