Investment Securities - Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Less than 12 months	$ 3,946	$ 1,400
12 months or longer	278	0
Total fair value	4,224	1,400
Unrealized Losses
Less than 12 months	(71)	(6)
12 months or longer	(10)	0
Total unrealized losses	(81)	(6)
U.S. treasuries
Schedule of Investments [Line Items]
Less than 12 months		307
12 months or longer		0
Total fair value		307
Unrealized Losses
Less than 12 months		0
12 months or longer		0
Total unrealized losses		0
Government agency issued MBS
Schedule of Investments [Line Items]
Less than 12 months	2,101	426
12 months or longer	99	0
Total fair value	2,200	426
Unrealized Losses
Less than 12 months	(33)	(2)
12 months or longer	(4)	0
Total unrealized losses	(37)	(2)
Government agency issued CMO
Schedule of Investments [Line Items]
Less than 12 months	1,243	586
12 months or longer	179	0
Total fair value	1,422	586
Unrealized Losses
Less than 12 months	(25)	(3)
12 months or longer	(6)	0
Total unrealized losses	(31)	(3)
Other U.S. government agencies
Schedule of Investments [Line Items]
Less than 12 months	495	80
12 months or longer	0	0
Total fair value	495	80
Unrealized Losses
Less than 12 months	(12)	(1)
12 months or longer	0	0
Total unrealized losses	(12)	(1)
States and municipalities
Schedule of Investments [Line Items]
Less than 12 months	107	1
12 months or longer	0	0
Total fair value	107	1
Unrealized Losses
Less than 12 months	(1)	0
12 months or longer	0	0
Total unrealized losses	$ (1)	$ 0