Credit Quality And Allowance For Credit Losses (Loans By Credit Quality Indicator and Vintage Year) (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		$ 52,369	$ 50,369
Financing Receivable, Originated in Current Fiscal Year		8,171
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		6,236
Financing Receivable, Originated Two Years before Latest Fiscal Year		4,869
Financing Receivable, Originated Three Years before Latest Fiscal Year		3,629
Financing Receivable, Originated Four Years before Latest Fiscal Year		2,216
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		4,817
Financing Receivable, Revolving		22,336
Financing Receivable, Revolving, Converted to Term Loan		95
Business loans | Commercial borrower
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		48,276	46,084
Financing Receivable, Originated in Current Fiscal Year		7,534
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		5,934
Financing Receivable, Originated Two Years before Latest Fiscal Year		4,710
Financing Receivable, Originated Three Years before Latest Fiscal Year		3,380
Financing Receivable, Originated Four Years before Latest Fiscal Year		1,981
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		4,273
Financing Receivable, Revolving		20,444
Financing Receivable, Revolving, Converted to Term Loan		20
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		32,604	31,473
Financing Receivable, Originated in Current Fiscal Year		5,252
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		2,838
Financing Receivable, Originated Two Years before Latest Fiscal Year		1,948
Financing Receivable, Originated Three Years before Latest Fiscal Year		1,293
Financing Receivable, Originated Four Years before Latest Fiscal Year		591
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		1,085
Financing Receivable, Revolving		19,577
Financing Receivable, Revolving, Converted to Term Loan		20
Business loans | Commercial borrower | Domestic loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	29,947	29,785
Financing Receivable, Originated in Current Fiscal Year	[1],[2]	5,220
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	2,522
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	1,712
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	1,176
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	496
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	887
Financing Receivable, Revolving	[1]	17,916
Financing Receivable, Revolving, Converted to Term Loan	[1]	18
Business loans | Commercial borrower | Domestic loans | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	2,657	1,688
Financing Receivable, Originated in Current Fiscal Year	[3]	32
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	316
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	236
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	117
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	95
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	198
Financing Receivable, Revolving	[3]	1,661
Financing Receivable, Revolving, Converted to Term Loan	[3]	2
Business loans | Commercial borrower | International loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		923	1,009
Financing Receivable, Originated in Current Fiscal Year		296
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		175
Financing Receivable, Originated Two Years before Latest Fiscal Year		126
Financing Receivable, Originated Three Years before Latest Fiscal Year		15
Financing Receivable, Originated Four Years before Latest Fiscal Year		10
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		66
Financing Receivable, Revolving		235
Financing Receivable, Revolving, Converted to Term Loan		0
Business loans | Commercial borrower | International loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	879	972
Financing Receivable, Originated in Current Fiscal Year	[1]	283
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	175
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	126
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	11
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	2
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	64
Financing Receivable, Revolving	[1]	218
Financing Receivable, Revolving, Converted to Term Loan	[1]	0
Business loans | Commercial borrower | International loans | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	44	37
Financing Receivable, Originated in Current Fiscal Year	[3]	13
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	4
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	8
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	2
Financing Receivable, Revolving	[3]	17
Financing Receivable, Revolving, Converted to Term Loan	[3]	0
Business loans | Real estate construction | Commercial borrower | Domestic loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		4,146	3,455
Financing Receivable, Originated in Current Fiscal Year		189
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		1,010
Financing Receivable, Originated Two Years before Latest Fiscal Year		1,328
Financing Receivable, Originated Three Years before Latest Fiscal Year		798
Financing Receivable, Originated Four Years before Latest Fiscal Year		435
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		192
Financing Receivable, Revolving		194
Financing Receivable, Revolving, Converted to Term Loan		0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	4,075	3,424
Financing Receivable, Originated in Current Fiscal Year	[1]	186
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	983
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	1,323
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	773
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	426
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	191
Financing Receivable, Revolving	[1]	193
Financing Receivable, Revolving, Converted to Term Loan	[1]	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	71	31
Financing Receivable, Originated in Current Fiscal Year	[3]	3
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	27
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	5
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	25
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	9
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	1
Financing Receivable, Revolving	[3]	1
Financing Receivable, Revolving, Converted to Term Loan	[3]	0
Business loans | Commercial mortgage | Commercial borrower | Domestic loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		10,002	9,559
Financing Receivable, Originated in Current Fiscal Year		1,701
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		1,767
Financing Receivable, Originated Two Years before Latest Fiscal Year		1,226
Financing Receivable, Originated Three Years before Latest Fiscal Year		1,219
Financing Receivable, Originated Four Years before Latest Fiscal Year		929
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		2,722
Financing Receivable, Revolving		438
Financing Receivable, Revolving, Converted to Term Loan		0
Business loans | Commercial mortgage | Commercial borrower | Domestic loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	9,473	9,262
Financing Receivable, Originated in Current Fiscal Year	[1]	1,662
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	1,649
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	1,185
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	1,161
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	880
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	2,509
Financing Receivable, Revolving	[1]	427
Financing Receivable, Revolving, Converted to Term Loan	[1]	0
Business loans | Commercial mortgage | Commercial borrower | Domestic loans | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	529	297
Financing Receivable, Originated in Current Fiscal Year	[3]	39
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	118
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	41
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	58
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	49
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	213
Financing Receivable, Revolving	[3]	11
Financing Receivable, Revolving, Converted to Term Loan	[3]	0
Business loans | Lease financing | Commercial borrower | Domestic loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		601	588
Financing Receivable, Originated in Current Fiscal Year		96
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		144
Financing Receivable, Originated Two Years before Latest Fiscal Year		82
Financing Receivable, Originated Three Years before Latest Fiscal Year		55
Financing Receivable, Originated Four Years before Latest Fiscal Year		16
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		208
Financing Receivable, Revolving		0
Financing Receivable, Revolving, Converted to Term Loan		0
Business loans | Lease financing | Commercial borrower | Domestic loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	574	579
Financing Receivable, Originated in Current Fiscal Year	[1]	94
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	126
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	78
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	53
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	15
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	208
Financing Receivable, Revolving	[1]	0
Financing Receivable, Revolving, Converted to Term Loan	[1]	0
Business loans | Lease financing | Commercial borrower | Domestic loans | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	27	9
Financing Receivable, Originated in Current Fiscal Year	[3]	2
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	18
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	4
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	2
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	0
Financing Receivable, Revolving	[3]	0
Financing Receivable, Revolving, Converted to Term Loan	[3]	0
Retail loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		4,093	4,285
Financing Receivable, Originated in Current Fiscal Year		637
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		302
Financing Receivable, Originated Two Years before Latest Fiscal Year		159
Financing Receivable, Originated Three Years before Latest Fiscal Year		249
Financing Receivable, Originated Four Years before Latest Fiscal Year		235
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		544
Financing Receivable, Revolving		1,892
Financing Receivable, Revolving, Converted to Term Loan		75
Retail loans | Consumer borrower
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		2,166	2,440
Financing Receivable, Originated in Current Fiscal Year		47
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		53
Financing Receivable, Originated Two Years before Latest Fiscal Year		20
Financing Receivable, Originated Three Years before Latest Fiscal Year		2
Financing Receivable, Originated Four Years before Latest Fiscal Year		7
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		70
Financing Receivable, Revolving		1,892
Financing Receivable, Revolving, Converted to Term Loan		75
Retail loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		1,927	1,845
Financing Receivable, Originated in Current Fiscal Year		590
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		249
Financing Receivable, Originated Two Years before Latest Fiscal Year		139
Financing Receivable, Originated Three Years before Latest Fiscal Year		247
Financing Receivable, Originated Four Years before Latest Fiscal Year		228
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		474
Financing Receivable, Revolving		0
Financing Receivable, Revolving, Converted to Term Loan		0
Retail loans | Residential mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	1,882	1,823
Financing Receivable, Originated in Current Fiscal Year	[1]	587
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	248
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	137
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	237
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	226
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	447
Financing Receivable, Revolving	[1]	0
Financing Receivable, Revolving, Converted to Term Loan	[1]	0
Retail loans | Residential mortgage | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	45	22
Financing Receivable, Originated in Current Fiscal Year	[3]	3
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	2
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	10
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	2
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	27
Financing Receivable, Revolving	[3]	0
Financing Receivable, Revolving, Converted to Term Loan	[3]	0
Retail loans | Home equity | Consumer borrower
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		1,640	1,711
Financing Receivable, Originated in Current Fiscal Year		0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		0
Financing Receivable, Originated Two Years before Latest Fiscal Year		0
Financing Receivable, Originated Three Years before Latest Fiscal Year		0
Financing Receivable, Originated Four Years before Latest Fiscal Year		0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		18
Financing Receivable, Revolving		1,547
Financing Receivable, Revolving, Converted to Term Loan		75
Retail loans | Home equity | Consumer borrower | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	1,617	1,682
Financing Receivable, Originated in Current Fiscal Year	[1]	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	17
Financing Receivable, Revolving	[1]	1,531
Financing Receivable, Revolving, Converted to Term Loan	[1]	69
Retail loans | Home equity | Consumer borrower | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	23	29
Financing Receivable, Originated in Current Fiscal Year	[3]	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	1
Financing Receivable, Revolving	[3]	16
Financing Receivable, Revolving, Converted to Term Loan	[3]	6
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		526	729
Financing Receivable, Originated in Current Fiscal Year		47
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year		53
Financing Receivable, Originated Two Years before Latest Fiscal Year		20
Financing Receivable, Originated Three Years before Latest Fiscal Year		2
Financing Receivable, Originated Four Years before Latest Fiscal Year		7
Financing Receivable, Originated Five or More Years before Latest Fiscal Year		52
Financing Receivable, Revolving		345
Financing Receivable, Revolving, Converted to Term Loan		0
Retail loans | Other consumer | Consumer borrower | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	516	722
Financing Receivable, Originated in Current Fiscal Year	[1]	47
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[1]	52
Financing Receivable, Originated Two Years before Latest Fiscal Year	[1]	17
Financing Receivable, Originated Three Years before Latest Fiscal Year	[1]	2
Financing Receivable, Originated Four Years before Latest Fiscal Year	[1]	7
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[1]	52
Financing Receivable, Revolving	[1]	339
Financing Receivable, Revolving, Converted to Term Loan	[1]	0
Retail loans | Other consumer | Consumer borrower | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[3]	10	$ 7
Financing Receivable, Originated in Current Fiscal Year	[3]	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	[3]	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	[3]	3
Financing Receivable, Originated Three Years before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	[3]	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	[3]	0
Financing Receivable, Revolving	[3]	6
Financing Receivable, Revolving, Converted to Term Loan	[3]	$ 0

[1] Includes all loans not included in the categories of special mention, substandard or nonaccrual.

[2] Includes $3.8 billion of Small Business Administration Paycheck Protection Program (PPP) loans at September 30, 2020.

[3] Includes loans with an internal rating of special mention, substandard loans for which the accrual of interest has not been discontinued and nonaccrual loans. Special mention loans have potential credit weaknesses that deserve management’s close attention, such as loans to borrowers who may be experiencing financial difficulties that may result in deterioration of repayment prospects from the borrower at some future date. Accruing substandard loans have a well-defined weakness, or weaknesses, such as loans to borrowers who may be experiencing losses from operations or inadequate liquidity of a degree and duration that jeopardizes the orderly repayment of the loan. Substandard loans are also distinguished by the distinct possibility of loss in the future if these weaknesses are not corrected. Nonaccrual loans are loans for which the accrual of interest has been discontinued. For further information regarding nonaccrual loans, refer to the Nonperforming Assets subheading in Note 1 - Basis of Presentation and Accounting Policies - on page F-51 in the Corporation's 2019 Annual Report. These categories are generally consistent with the "special mention" and "substandard" categories as defined by regulatory authorities. A minority of nonaccrual loans are consistent with the "doubtful" category.