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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses	$ 44	$ (29)	$ 31	$ (17)
Total loans					$ 51,801	$ 50,163
Financing Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	647	698	671	712
Loan charge-offs	(44)	(20)	(64)	(57)
Recoveries on loans previously charged-off	11	23	20	32
Net loan recoveries (charge-offs)	(33)	3	(44)	(25)
Provision for loan losses	43	(23)	30	(9)
Balance at end of period	657	677	657	677
As a percentage of total loans					1.27%		1.36%
Allowance for loan losses individually evaluated for impairment					$ 39		$ 39
Allowance for loan losses collectively evaluated for impairment					618		638
Total allowance for loan losses	647	698	671	712	657	671	677
Loans individually evaluated for impairment					240		340
Loans collectively evaluated for impairment					51,561		49,452
Total loans					$ 51,801		$ 49,792
Allowance for Loan and Lease Losses, Foreign Currency Translation	0	(1)	0	(1)
Business loans | Financing Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	608	653	627	661
Loan charge-offs	(43)	(18)	(62)	(54)
Recoveries on loans previously charged-off	10	22	18	30
Net loan recoveries (charge-offs)	(33)	4	(44)	(24)
Provision for loan losses	43	(21)	35	(1)
Balance at end of period	618	635	618	635
As a percentage of total loans					1.30%		1.40%
Allowance for loan losses individually evaluated for impairment					$ 38		$ 39
Allowance for loan losses collectively evaluated for impairment					580		596
Total allowance for loan losses	608	653	627	661	618	627	635
Loans individually evaluated for impairment					207		310
Loans collectively evaluated for impairment					47,227		45,052
Total loans					47,434		$ 45,362
Allowance for Loan and Lease Losses, Foreign Currency Translation	0	(1)	0	(1)
Retail loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans					$ 4,367	4,484
Retail loans | Financing Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	39	45	44	51
Loan charge-offs	(1)	(2)	(2)	(3)
Recoveries on loans previously charged-off	1	1	2	2
Net loan recoveries (charge-offs)	0	(1)	0	(1)
Provision for loan losses	0	(2)	(5)	(8)
Balance at end of period	39	42	39	42
As a percentage of total loans					0.89%		0.96%
Allowance for loan losses individually evaluated for impairment					$ 1		$ 0
Allowance for loan losses collectively evaluated for impairment					38		42
Total allowance for loan losses	39	45	39	42	39	$ 44	42
Loans individually evaluated for impairment					33		30
Loans collectively evaluated for impairment					4,334		4,400
Total loans					$ 4,367		$ 4,430
Allowance for Loan and Lease Losses, Foreign Currency Translation	$ 0	$ 0	$ 0	$ 0