Investment Securities - Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Less than 12 months	$ 3,767	$ 1,400
12 months or longer	0	0
Total fair value	3,767	1,400
Unrealized Losses
Less than 12 months	(94)	(6)
12 months or longer	0	0
Total unrealized losses	(94)	(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	1,772	426
12 months or longer	0	0
Total fair value	1,772	426
Unrealized Losses
Less than 12 months	(39)	(2)
12 months or longer	0	0
Total unrealized losses	(39)	(2)
Government agency issued CMO
Schedule of Investments [Line Items]
Less than 12 months	1,508	586
12 months or longer	0	0
Total fair value	1,508	586
Unrealized Losses
Less than 12 months	(41)	(3)
12 months or longer	0	0
Total unrealized losses	(41)	(3)
Other U.S. government agencies
Schedule of Investments [Line Items]
Less than 12 months	405	80
12 months or longer	0	0
Total fair value	405	80
Unrealized Losses
Less than 12 months	(13)	(1)
12 months or longer	0	0
Total unrealized losses	(13)	(1)
States and municipalities
Schedule of Investments [Line Items]
Less than 12 months	82	1
12 months or longer	0	0
Total fair value	82	1
Unrealized Losses
Less than 12 months	(1)	0
12 months or longer	0	0
Total unrealized losses	$ (1)	$ 0