Loans And Allowance For Credit Losses (Summary Of Major Portfolio Segment And Specific Loan Class) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	$ 544	$ 612
Loans held for sale	128		$ 172
Commercial and industrial	13,368		13,452
Leasing	404		423
Owner occupied	6,973		6,962
Municipal	811		778
Construction and land development	2,123		2,019
Term	9,083		9,322
Provision for loan losses	(23)	(42)
Allowance for Loan and Lease Losses, Write-offs	(57)	(48)
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	11	12
Net loan and lease charge-offs	(46)	(36)
Reserve for unfunded lending commitments	60	69	65	$ 75
Provision for Unfunded Lending Commitments	5	6
Total allowance for credit losses	604	$ 681
Loans Receivable, Gross, Commercial, Real Estate	11,206		11,341
Loans and Leases Receivable, Gross, Consumer, Home Equity	2,638		2,645
Loans and Leases Receivable, Gross, Consumer, Mortgage	6,185		5,891
Loans and Leases Receivable, Gross, Consumer, Construction	517		486
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	459		481
Loans and Leases Receivable, Gross, Consumer, Other	181		190
Loans and Leases Receivable, Gross	42,742		42,649
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable before Fees, Gross	21,556		21,615
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable before Fees, Gross	$ 9,980		$ 9,693

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of other addition (reduction) in allowance reserve for credit loss.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount before allowance of commercial leases and leveraged lease transactions where the entity is long-term creditor. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes leases covered under loss sharing agreements.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases issued to a unit or agency of a federal, state or local jurisdiction within the country of domicile of the reporting entity. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of loans issued to build, improve or remodel a residential home. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of revolving, open-end loan, extended under a line of credit and secured by the borrower's residential property. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of consumer mortgage. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes subordinated loans such as home equity lines of credit and loans and leases covered under loss sharing agreements.

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Amount before allowance of consumer loans and leases not otherwise specified in the taxonomy. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of credit card loans issued to individuals. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of loans issued to commercial and industrial institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes real estate loans and loans covered under loss sharing agreements.

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Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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Amount of expense related to estimated loss from loan and lease transactions.

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Allowance for loan and lease losses and reserve for unfunded lending commitments

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Commercial lending loans - owner occupied

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Commercial real estate term loans

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Land Development Loans, Loans receivable commercial construction and land development

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Estimated reserve for unfunded lending commitments.

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Provision recorded in operations to increase or decrease the estimated reserve for unfunded lending commitments.

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