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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jan. 01, 2021	Jan. 01, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 807	$ 978	$ 992	$ 668
Provision for credit losses	(135)	138	(317)	549
Balance at end of period	$ 683	$ 1,066	$ 683	$ 1,066
As a percentage of total loans	1.36%	1.99%	1.36%	1.99%
As a percentage of total loans excluding PPP Loans	1.44%	2.15%	1.44%	2.15%
Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Reduction in business loans allowance for credit losses					$ 0	$ (42)
Increase in retail loans allowance for credit losses					0	25
Day-one decrease in the overall allowance for credit losses					$ 0	$ (17)
Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 777	$ 916	$ 948	$ 637
Loan charge-offs	(8)	(57)	(24)	(146)
Recoveries on loans previously charged-off	19	7	32	12
Net loan charge-offs	11	(50)	8	(134)
Provision for credit losses	(136)	141	(304)	521
Balance at end of period	$ 652	$ 1,007	$ 652	$ 1,007
As a percentage of total loans	1.30%	1.88%	1.30%	1.88%
As a percentage of total loans excluding PPP Loans	1.37%	2.03%	1.37%	2.03%
Unused Commitments to Extend Credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 30	$ 62	$ 44	$ 31
Provision for credit losses	1	(3)	(13)	28
Balance at end of period	31	59	31	59
Business loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	731	913	930	629
Provision for credit losses	(130)	130	(326)	538
Balance at end of period	$ 613	$ 993	$ 613	$ 993
As a percentage of total loans	1.32%	2.01%	1.32%	2.01%
As a percentage of total loans excluding PPP Loans	1.41%	2.18%	1.41%	2.18%
Business loans | Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 709	$ 861	$ 895	$ 601
Loan charge-offs	(7)	(56)	(22)	(143)
Recoveries on loans previously charged-off	19	6	31	11
Net loan charge-offs	12	(50)	9	(132)
Provision for credit losses	(132)	132	(315)	516
Balance at end of period	$ 589	$ 943	$ 589	$ 943
As a percentage of total loans	1.27%	1.91%	1.27%	1.91%
As a percentage of total loans excluding PPP Loans	1.35%	2.07%	1.35%	2.07%
Business loans | Unused Commitments to Extend Credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 22	$ 52	$ 35	$ 28
Provision for credit losses	2	(2)	(11)	22
Balance at end of period	24	50	24	50
Retail loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	76	65	62	39
Provision for credit losses	(5)	8	9	11
Balance at end of period	$ 70	$ 73	$ 70	$ 73
As a percentage of total loans	1.80%	1.82%	1.80%	1.82%
Retail loans | Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 68	$ 55	$ 53	$ 36
Loan charge-offs	(1)	(1)	(2)	(3)
Recoveries on loans previously charged-off	0	1	1	1
Net loan charge-offs	(1)	0	(1)	(2)
Provision for credit losses	(4)	9	11	5
Balance at end of period	$ 63	$ 64	$ 63	$ 64
As a percentage of total loans	1.63%	1.59%	1.63%	1.59%
Retail loans | Unused Commitments to Extend Credit
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	$ 8	$ 10	$ 9	$ 3
Provision for credit losses	(1)	(1)	(2)	6
Balance at end of period	$ 7	$ 9	$ 7	$ 9