Allowances for Loan and Lease Losses (Rollforward of Allowance For Loan and Lease Losses and Associated Loan Data) (Details)	3 Months Ended			6 Months Ended
	Jun. 30, 2019 USD ($) segment		Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment		Jun. 30, 2018 USD ($)	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				(442,000,000)		(386,000,000)
Recoveries				164,000,000		164,000,000
Net (charge-offs)				(278,000,000)		(222,000,000)
Provision for credit losses	$ 180,000,000		$ 80,000,000	369,000,000		172,000,000
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit				(6,000,000)		8,000,000
Other				7,000,000		12,000,000
Ending Balance	2,721,000,000		2,581,000,000	2,721,000,000		2,581,000,000
Loans collectively evaluated for impairment - associated allowance	2,230,000,000		2,064,000,000	2,230,000,000		2,064,000,000
Impaired loans - associated allowance	209,000,000			209,000,000			$ 209,000,000
Loans collectively evaluated for impairment	232,525,000,000		217,783,000,000	232,525,000,000		217,783,000,000
Fair value option loans	755,000,000		753,000,000	755,000,000		753,000,000
Purchased impaired loans	1,871,000,000		2,211,000,000	1,871,000,000		2,211,000,000
Total loans	$ 237,215,000,000	[1]	$ 222,855,000,000	$ 237,215,000,000	[1]	$ 222,855,000,000	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	$ 156,000,000		$ 176,000,000	$ 156,000,000		$ 176,000,000
Loans individually evaluated for impairment	1,777,000,000		1,868,000,000	1,777,000,000		1,868,000,000
Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	53,000,000		60,000,000	53,000,000		60,000,000
Loans individually evaluated for impairment	287,000,000		240,000,000	287,000,000		240,000,000
Purchased Impaired Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance	282,000,000		281,000,000	282,000,000		281,000,000
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				(84,000,000)		(64,000,000)
Recoveries				40,000,000		51,000,000
Net (charge-offs)				(44,000,000)		(13,000,000)
Provision for credit losses				187,000,000		56,000,000
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit				(7,000,000)		6,000,000
Other						(1,000,000)
Ending Balance	1,799,000,000		1,630,000,000	1,799,000,000		1,630,000,000
Loans collectively evaluated for impairment - associated allowance	1,713,000,000		1,541,000,000	1,713,000,000		1,541,000,000
Impaired loans - associated allowance	86,000,000			86,000,000			73,000,000
Loans collectively evaluated for impairment	160,920,000,000		149,072,000,000	160,920,000,000		149,072,000,000
Total loans	$ 161,603,000,000		$ 149,636,000,000	$ 161,603,000,000		$ 149,636,000,000	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	1.11%		1.09%	1.11%		1.09%
Total commercial lending [Member] | TDRs [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	$ 33,000,000		$ 29,000,000	$ 33,000,000		$ 29,000,000
Loans individually evaluated for impairment	396,000,000		324,000,000	396,000,000		324,000,000
Total commercial lending [Member] | Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	53,000,000		60,000,000	53,000,000		60,000,000
Loans individually evaluated for impairment	287,000,000		240,000,000	287,000,000		240,000,000
Total consumer lending [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance				966,000,000		1,029,000,000
Charge-offs				(358,000,000)		(322,000,000)
Recoveries				124,000,000		113,000,000
Net (charge-offs)				(234,000,000)		(209,000,000)
Provision for credit losses				182,000,000		116,000,000
Net (increase) / decrease in allowance for unfunded loan commitments and letters of credit				1,000,000		2,000,000
Other				7,000,000		13,000,000
Ending Balance	922,000,000		951,000,000	922,000,000		951,000,000
Loans collectively evaluated for impairment - associated allowance	517,000,000		523,000,000	517,000,000		523,000,000
Impaired loans - associated allowance	123,000,000			123,000,000			136,000,000
Loans collectively evaluated for impairment	71,605,000,000		68,711,000,000	71,605,000,000		68,711,000,000
Fair value option loans	755,000,000		753,000,000	755,000,000		753,000,000
Purchased impaired loans	1,871,000,000		2,211,000,000	1,871,000,000		2,211,000,000
Total loans	$ 75,612,000,000		$ 73,219,000,000	$ 75,612,000,000		$ 73,219,000,000	$ 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	1.22%		1.30%	1.22%		1.30%
Total consumer lending [Member] | TDRs [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans individually evaluated for impairment - associated allowance	$ 123,000,000		$ 147,000,000	$ 123,000,000		$ 147,000,000
Loans individually evaluated for impairment	1,381,000,000		1,544,000,000	1,381,000,000		1,544,000,000
Total consumer lending [Member] | Purchased Impaired Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Impaired loans - associated allowance	$ 282,000,000		$ 281,000,000	$ 282,000,000		$ 281,000,000

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.1 billion, Loans of $.8 billion and Other assets of $.1 billion at June 30, 2019 and Loans held for sale of $.9 billion, Loans of $.8 billion and Other assets of $.2 billion at December 31, 2018.