Credit Quality And Allowance For Credit Losses (Changes In The Allowance For Loan Losses And Related Loan Amounts) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020	Jan. 01, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 1,066	$ 688	$ 668	$ 701
Increase in retail loans allowance for credit losses					$ 25
Provision for credit losses	5	35	554	66
Balance at end of period	$ 1,038	$ 681	$ 1,038	$ 681
As a percentage of total loans	1.98%	1.32%	1.98%	1.32%
As a percentage of total loans excluding PPP Loans	2.14%		2.14%
Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Reduction in business loans allowance for credit losses					(42)	$ 0
Increase in retail loans allowance for credit losses					25	0
Day-one decrease in the overall allowance for credit losses					$ (17)	$ 0
Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 1,007	$ 657	$ 637	$ 671
Loan charge-offs	(53)	(61)	(199)	(125)
Recoveries on loans previously charged-off	20	19	32	39
Net loan charge-offs	(33)	(42)	(167)	(86)
Provision for credit losses	4	37	525	67
Balance at end of period	$ 978	$ 652	$ 978	$ 652
As a percentage of total loans	1.87%	1.27%	1.87%	1.27%
As a percentage of total loans excluding PPP Loans	2.01%		2.01%
Unused Commitments to Extend Credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 59	$ 31	$ 31	$ 30
Provision for credit losses	1	(2)	29	(1)
Balance at end of period	60	29	60	29
Business loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	993	646	629	653
Provision for credit losses	16	37	554	74
Balance at end of period	$ 974	$ 641	$ 974	$ 641
As a percentage of total loans	2.02%	1.36%	2.02%	1.36%
As a percentage of total loans excluding PPP Loans	2.19%		2.19%
Business loans | Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 943	$ 618	$ 601	$ 627
Loan charge-offs	(53)	(59)	(196)	(121)
Recoveries on loans previously charged-off	18	17	29	35
Net loan charge-offs	(35)	(42)	(167)	(86)
Provision for credit losses	15	39	531	74
Balance at end of period	$ 923	$ 615	$ 923	$ 615
As a percentage of total loans	1.91%	1.30%	1.91%	1.30%
As a percentage of total loans excluding PPP Loans	2.07%		2.07%
Business loans | Unused Commitments to Extend Credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 50	$ 28	$ 28	$ 26
Provision for credit losses	1	(2)	23	0
Balance at end of period	51	26	51	26
Retail loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	73	42	39	48
Provision for credit losses	(11)	(2)	0	8
Balance at end of period	$ 64	$ 40	$ 64	$ 40
As a percentage of total loans	1.57%	0.92%	1.57%	0.92%
Retail loans | Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 64	$ 39	$ 36	$ 44
Loan charge-offs	0	(2)	(3)	(4)
Recoveries on loans previously charged-off	2	2	3	4
Net loan charge-offs	2	0	0	0
Provision for credit losses	(11)	(2)	(6)	(7)
Balance at end of period	$ 55	$ 37	$ 55	$ 37
As a percentage of total loans	1.35%	0.86%	1.35%	0.86%
Retail loans | Unused Commitments to Extend Credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 9	$ 3	$ 3	$ 4
Provision for credit losses	0	0	6	(1)
Balance at end of period	$ 9	$ 3	$ 9	$ 3