Loans And Allowance For Credit Losses (Schedule Of Investment Of Accruing And Nonaccruing Loans Modified As Troubled Debt Restructurings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 1	$ 7	$ 2	$ 7	$ 84	$ 139
Accruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	4	0	4
Nonaccruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	1	3	2	3
Commercial And Industrial [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	1	3	1	3
Commercial And Industrial [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	0	0	0
Commercial And Industrial [Member] | Nonaccruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	1	3	1	3
Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	4	1	4
Owner Occupied [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	4	0	4
Owner Occupied [Member] | Nonaccruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	0	1	0
Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	1	7	2	7
Commercial Loan [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	0	4	0	4
Commercial Loan [Member] | Nonaccruing [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 1	$ 3	$ 2	$ 3