Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net gains (losses) on financial instruments at fair value and foreign exchange	$ (38)	$ 52	$ (17)
Income (loss) before income taxes	(578)	(357)	(296)
Net income (loss)	(578)	(359)	(296)
Amounts reclassified from AOCI [Member]
Net income (loss)	13	(40)	0
Unrealized gains (losses) on AFS, net [Member]
Net income (loss)	19	(12)	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	19	14	6
Net investment losses related to OTTI	0	(25)	(5)
Net investment income	0	(1)	(1)
Income (loss) before income taxes	19	(12)	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	$ (6)	$ (28)	$ 0