Accumulated Other Comprehensive Income (Changes In The Components Of AOCI) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Beginning balance	$ (2)	$ (156)	$ (19)
Other comprehensive income (loss) before reclassifications	130	114
Amounts reclassified from AOCI	(13)	40
Total other comprehensive income (loss)	117	154	30
Ending balance	115	(2)	(156)
Unrealized gains (losses) on AFS, net [Member]
Beginning balance	112	(39)	(10)
Other comprehensive income (loss) before reclassifications	83	139
Amounts reclassified from AOCI	(19)	12
Total other comprehensive income (loss)	64	151	(24)
Ending balance	176	112	(39)
Unrealized gains (losses) on AFS, net [Member] | ASU 2016-01
ASU transition adjustment			(2)
Unrealized gains (losses) on AFS, net [Member] | ASU 2018-02
ASU transition adjustment			(3)
Foreign currency translation, net [Member]
Beginning balance	(7)	(7)	(9)
Other comprehensive income (loss) before reclassifications	(3)	0
Amounts reclassified from AOCI	0	0
Total other comprehensive income (loss)	(3)	0	2
Ending balance	(10)	(7)	(7)
Foreign currency translation, net [Member] | ASU 2016-01
ASU transition adjustment			0
Foreign currency translation, net [Member] | ASU 2018-02
ASU transition adjustment			0
Instrument-specific credit risk of liabilities measured at fair value, net [Member]
Beginning balance	(107)	(110)	0
Other comprehensive income (loss) before reclassifications	50	(25)
Amounts reclassified from AOCI	6	28
Total other comprehensive income (loss)	56	3	52
Ending balance	(51)	(107)	(110)
Instrument-specific credit risk of liabilities measured at fair value, net [Member] | ASU 2016-01
ASU transition adjustment			(162)
Instrument-specific credit risk of liabilities measured at fair value, net [Member] | ASU 2018-02
ASU transition adjustment			0
AOCI Attributable to Parent [Member]
Total other comprehensive income (loss)	117	154	30
AOCI Attributable to Parent [Member] | ASU 2016-01
ASU transition adjustment	0	0	(164)
AOCI Attributable to Parent [Member] | ASU 2018-02
ASU transition adjustment	$ 0	$ 0	$ (3)