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
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Jan. 01, 2020	Mar. 31, 2019	Jan. 01, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for loan losses	$ 411	$ (13)
Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	637	671
Loan charge-offs	(89)	(20)
Recoveries on loans previously charged-off	5	9
Net loan charge-offs	(84)	(11)
Provision for loan losses	380	(13)
Balance at end of period	916	647
As a percentage of total loans			1.71%		1.29%
Total allowance for loan losses	916	647	$ 916		$ 647
Business loans | Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	601	627
Loan charge-offs	(87)	(19)
Recoveries on loans previously charged-off	5	8
Net loan charge-offs	(82)	(11)
Provision for loan losses	384	(8)
Balance at end of period	861	608
As a percentage of total loans			1.75%		1.33%
Total allowance for loan losses	861	608	$ 861		$ 608
Retail loans | Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	36	44
Loan charge-offs	(2)	(1)
Recoveries on loans previously charged-off	0	1
Net loan charge-offs	(2)	0
Provision for loan losses	(4)	(5)
Balance at end of period	55	39
As a percentage of total loans			1.35%		0.88%
Total allowance for loan losses	$ 55	$ 39	$ 55		$ 39
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