Loans And Allowance For Credit Losses (Summary Of Major Portfolio Segment And Specific Loan Class) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	$ 510	$ 480	$ 510	$ 480
Loans held for sale	141		141			$ 93
Loans Credit Quality Outstanding, Commercial And Industrial	14,846		14,846			14,513
Loan Credit Quality Outstanding, Leasing	332		332			327
Owner occupied	7,924		7,924			7,661
Loans Credit Quality Outstanding, Municipal	2,185		2,185			1,661
Land Development Loans, Loans Receivable Commercial Construction and Land Development	2,347		2,347			2,186
Term	9,469		9,469			8,939
Loans Credit Quality Outstanding, Commercial Real Estate	11,816		11,816			11,125
Provision for loan losses	(8)	(11)	(30)	(46)
Allowance for Loan and Lease Losses, Write-offs	(11)	(17)	(46)	(56)
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	10	18	31	64
Net loan and lease charge-offs	1	(1)	15	(8)
Reserve for unfunded lending commitments	62	58	62	58	$ 60	57	$ 58	$ 58
Provision for Unfunded Lending Commitments (decrease)	2	0	5	0
Allowance for loan and lease losses and reserve for unfunded lending commitments	572	$ 538	572	$ 538
Loans Credit Quality Outstanding, Home Equity Credit Line	2,930		2,930			2,937
Loans Credit Quality Outstanding, 1-4 Family Residential	7,506		7,506			7,176
Loans Credit Quality Outstanding, Construction and Other	637		637			643
Loans Credit Quality Outstanding, Bankcard	494		494			491
Loans Credit Quality Outstanding, Other	165		165			180
Loans and Leases Receivable, Gross	48,835		48,835			46,714
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, before Fees, Gross	25,287		25,287			24,162
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 11,732		$ 11,732			$ 11,427