Allowances for Loan and Lease Losses (Rollforward of Allowance For Loan and Lease Losses and Associated Loan Data) (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2019 USD ($) segment		Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment		Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of portfolio segments | segment	2			2
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				$ 2,629,000,000		$ 2,611,000,000
Charge-offs				(683,000,000)		(564,000,000)
Recoveries				250,000,000		251,000,000
Net (charge-offs)				(433,000,000)		(313,000,000)
Provision for credit losses	$ 183,000,000		$ 88,000,000	552,000,000		260,000,000
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit				(19,000,000)		9,000,000
Other				9,000,000		17,000,000
Ending Balance	2,738,000,000		2,584,000,000	2,738,000,000		2,584,000,000
Loans collectively evaluated for impairment - associated allowance	2,284,000,000		2,100,000,000	2,284,000,000		2,100,000,000
Impaired loans - associated allowance	176,000,000			176,000,000			$ 209,000,000
Loans collectively evaluated for impairment	232,801,000,000		218,106,000,000	232,801,000,000		218,106,000,000
Fair value option loans	754,000,000		753,000,000	754,000,000		753,000,000
Purchased impaired loans	1,794,000,000		2,102,000,000	1,794,000,000		2,102,000,000
Total loans	$ 237,377,000,000	[1]	$ 223,053,000,000	$ 237,377,000,000	[1]	$ 223,053,000,000	226,245,000,000	[1]
Portfolio segment ALLL as a percentage of total ALLL	100.00%		100.00%	100.00%		100.00%
Ratio of the allowance for loan and lease losses to total loans	1.15%		1.16%	1.15%		1.16%
TDRs [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	$ 129,000,000		$ 173,000,000	$ 129,000,000		$ 173,000,000
Loans individually evaluated for impairment	1,763,000,000		1,886,000,000	1,763,000,000		1,886,000,000
Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	47,000,000		37,000,000	47,000,000		37,000,000
Loans individually evaluated for impairment	265,000,000		206,000,000	265,000,000		206,000,000
Purchased Impaired Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance	278,000,000		274,000,000	278,000,000		274,000,000
Loans Accounted for under Fair Value Option [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans collectively evaluated for impairment - associated allowance	0			0
Total commercial lending [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				1,663,000,000		1,582,000,000
Charge-offs				(138,000,000)		(92,000,000)
Recoveries				59,000,000		74,000,000
Net (charge-offs)				(79,000,000)		(18,000,000)
Provision for credit losses				247,000,000		48,000,000
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit				(20,000,000)		7,000,000
Other						(1,000,000)
Ending Balance	1,811,000,000		1,618,000,000	1,811,000,000		1,618,000,000
Loans collectively evaluated for impairment - associated allowance	1,730,000,000		1,553,000,000	1,730,000,000		1,553,000,000
Impaired loans - associated allowance	81,000,000			81,000,000			73,000,000
Loans collectively evaluated for impairment	159,503,000,000		148,853,000,000	159,503,000,000		148,853,000,000
Total loans	$ 160,188,000,000		$ 149,448,000,000	$ 160,188,000,000		$ 149,448,000,000	152,282,000,000
Portfolio segment ALLL as a percentage of total ALLL	66.00%		63.00%	66.00%		63.00%
Ratio of the allowance for loan and lease losses to total loans	1.13%		1.08%	1.13%		1.08%
Total commercial lending [Member] | TDRs [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	$ 34,000,000		$ 28,000,000	$ 34,000,000		$ 28,000,000
Loans individually evaluated for impairment	420,000,000		389,000,000	420,000,000		389,000,000
Total commercial lending [Member] | Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	47,000,000		37,000,000	47,000,000		37,000,000
Loans individually evaluated for impairment	265,000,000		206,000,000	265,000,000		206,000,000
Total consumer lending [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				966,000,000		1,029,000,000
Charge-offs				(545,000,000)		(472,000,000)
Recoveries				191,000,000		177,000,000
Net (charge-offs)				(354,000,000)		(295,000,000)
Provision for credit losses				305,000,000		212,000,000
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit				1,000,000		2,000,000
Other				9,000,000		18,000,000
Ending Balance	927,000,000		966,000,000	927,000,000		966,000,000
Loans collectively evaluated for impairment - associated allowance	554,000,000		547,000,000	554,000,000		547,000,000
Impaired loans - associated allowance	95,000,000			95,000,000			136,000,000
Loans collectively evaluated for impairment	73,298,000,000		69,253,000,000	73,298,000,000		69,253,000,000
Fair value option loans	754,000,000		753,000,000	754,000,000		753,000,000
Purchased impaired loans	1,794,000,000		2,102,000,000	1,794,000,000		2,102,000,000
Total loans	$ 77,189,000,000		$ 73,605,000,000	$ 77,189,000,000		$ 73,605,000,000	$ 73,963,000,000
Portfolio segment ALLL as a percentage of total ALLL	34.00%		37.00%	34.00%		37.00%
Ratio of the allowance for loan and lease losses to total loans	1.20%		1.31%	1.20%		1.31%
Total consumer lending [Member] | TDRs [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	$ 95,000,000		$ 145,000,000	$ 95,000,000		$ 145,000,000
Loans individually evaluated for impairment	1,343,000,000		1,497,000,000	1,343,000,000		1,497,000,000
Total consumer lending [Member] | Purchased Impaired Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance	$ 278,000,000		$ 274,000,000	$ 278,000,000		$ 274,000,000

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.5 billion, Loans of $.8 billion and Other assets of $.1 billion at September 30, 2019 and Loans held for sale of $.9 billion, Loans of $.8 billion and Other assets of $.2 billion at December 31, 2018.