Investment Securities - Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Unrealized Losses
Fair value, less than 12 months	$ 1,400	$ 656
Unrealized losses, less than 12 months	(6)	(4)
Fair value, 12 months or longer	0	554
Unrealized loss, 12 months or longer	0	(7)
Fair value, total	1,400	1,210
Unrealized losses, total	(6)	(11)
U.S. treasuries
Unrealized Losses
Fair value, less than 12 months	307
Unrealized losses, less than 12 months	0
Fair value, 12 months or longer	0
Unrealized loss, 12 months or longer	0
Fair value, total	307
Unrealized losses, total	0
Government agency issued MBS
Unrealized Losses
Fair value, less than 12 months	426	175
Unrealized losses, less than 12 months	(2)	(1)
Fair value, 12 months or longer	0	193
Unrealized loss, 12 months or longer	0	(2)
Fair value, total	426	368
Unrealized losses, total	(2)	(3)
Government agency issued CMO
Unrealized Losses
Fair value, less than 12 months	586	379
Unrealized losses, less than 12 months	(3)	(2)
Fair value, 12 months or longer	0	361
Unrealized loss, 12 months or longer	0	(5)
Fair value, total	586	740
Unrealized losses, total	(3)	(7)
Other U.S. government agencies
Unrealized Losses
Fair value, less than 12 months	80	98
Unrealized losses, less than 12 months	(1)	(1)
Fair value, 12 months or longer	0	0
Unrealized loss, 12 months or longer	0	0
Fair value, total	80	98
Unrealized losses, total	(1)	(1)
States and municipalities
Unrealized Losses
Fair value, less than 12 months	1	4
Unrealized losses, less than 12 months	0	0
Fair value, 12 months or longer	0	0
Unrealized loss, 12 months or longer	0	0
Fair value, total	1	4
Unrealized losses, total	$ 0	$ 0