Loans And Allowance For Credit Losses (Summary Of Major Portfolio Segment And Specific Loan Class) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	$ 497	$ 473
Loans held for sale	69		$ 93
Loans Credit Quality Outstanding, Commercial And Industrial	14,758		14,513
Loan Credit Quality Outstanding, Leasing	312		327
Owner occupied	7,754		7,661
Loans Credit Quality Outstanding, Municipal	1,774		1,661
Land Development Loans, Loans Receivable Commercial Construction and Land Development	2,343		2,186
Term	9,187		8,939
Loans Credit Quality Outstanding, Commercial Real Estate	11,530		11,125
Provision for loan losses	(2)	40
Allowance for Loan and Lease Losses, Write-offs	12	26
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	12	21
Net loan and lease charge-offs	0	5
Reserve for unfunded lending commitments	59	51	57	$ 58
Provision for Unfunded Lending Commitments (decrease)	2	(7)
Allowance for loan and lease losses and reserve for unfunded lending commitments	556	$ 524
Loans Credit Quality Outstanding, Home Equity Credit Line	2,884		2,937
Loans Credit Quality Outstanding, 1-4 Family Residential	7,294		7,176
Loans Credit Quality Outstanding, Construction and Other	636		643
Loans Credit Quality Outstanding, Bankcard	489		491
Loans Credit Quality Outstanding, Other	175		180
Loans and Leases Receivable, Gross	47,606		46,714
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, before Fees, Gross	24,598		24,162
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 11,478		$ 11,427