Loans And Allowance For Credit Losses (Summary Of ALLL And Outstanding Loan Balances According To The Company's Impairment Method) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Current Fiscal Year End Date	--12-31
Allowance for loan losses: Individually evaluated for impairment	$ (31)	$ (65)
Allowance for loan losses: Collectively evaluated for impairment	487	502
Allowance for loan losses: Purchased loans with evidence of credit deterioration		0
Financing Receivable, Allowance for Credit Losses	0
Allowance for loan losses: Total	518	567	$ 606
Loans and Leases Receivable, Gross	44,780	42,649
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Individually evaluated for impairment	(26)	(56)
Allowance for loan losses: Collectively evaluated for impairment	345	364
Financing Receivable, Allowance for Credit Losses	0	0
Allowance for loan losses: Total	371	420	454
Outstanding loan balances: Individually evaluated for impairment		466
Outstanding loan balances: Collectively evaluated for impairment		21,111
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Individually evaluated for impairment		(3)
Allowance for loan losses: Collectively evaluated for impairment		113
Outstanding loan balances: Individually evaluated for impairment		78
Outstanding loan balances: Collectively evaluated for impairment		11,231
Loans and Leases Receivable, Gross	11,124	11,341
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Individually evaluated for impairment	(1)
Allowance for loan losses: Collectively evaluated for impairment	102
Financing Receivable, Allowance for Credit Losses	0	0
Allowance for loan losses: Total	103	116	114
Loans and Leases Receivable, Gross	2,021	2,019
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Individually evaluated for impairment	(4)	(6)
Allowance for loan losses: Collectively evaluated for impairment	40	25
Financing Receivable, Allowance for Credit Losses	0	0
Allowance for loan losses: Total	44	31	$ 38
Outstanding loan balances: Individually evaluated for impairment		75
Outstanding loan balances: Collectively evaluated for impairment		9,611
Loans and Leases Receivable, Gross	185	190
Outstanding Loan Balances [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Outstanding loan balances: Individually evaluated for impairment	459	619
Outstanding loan balances: Collectively evaluated for impairment	44,294	41,953
Loans and Leases Receivable, Gross	44,780	42,649
Financing Receivable, Acquired Deteriorated Credit Quality		77
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	27
Outstanding Loan Balances [Member] \| Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Outstanding loan balances: Individually evaluated for impairment	314
Outstanding loan balances: Collectively evaluated for impairment	22,598
Loans and Leases Receivable, Gross	22,926	21,615
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	14	38
Outstanding Loan Balances [Member] \| Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Outstanding loan balances: Individually evaluated for impairment	69
Outstanding loan balances: Collectively evaluated for impairment	11,048
Loans and Leases Receivable, Gross	11,124	11,341
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	7	32
Outstanding Loan Balances [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Outstanding loan balances: Individually evaluated for impairment	76
Outstanding loan balances: Collectively evaluated for impairment	10,648
Loans and Leases Receivable, Gross	10,730	9,693
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	$ 6	$ 7

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- Definition

The recorded amount of loans and debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it was probable, at acquisition, that the investor would be unable to collect all contractually required payments receivable. They are deemed to be impaired since the acquisition and an allowance for credit losses has been recorded. Disclosure is gross of the allowance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5275-111524

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A valuation allowance for financing receivables that are expected to be uncollectible.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
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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.

+ References

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Allowance for loan losses associated with purchased loans with evidence of credit deterioration.

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