Loans and Related Allowance for Credit Losses (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Loans	$ 249,279	$ 239,843
% of Loans	100.00%	100.00%
Unearned income, unamortized deferred fees and costs on originated loans, and premiums or discounts on purchased loans	$ 1,400	$ 1,100
Collateral Dependent [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,200
Other Assets [Member]
Financing Receivable, Past Due [Line Items]
Financing receivable, accrued interest	700
Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 245,393	$ 234,819
% of Loans	98.43%	97.90%
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 539	$ 661
% of Loans	0.22%	0.28%
60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 251	$ 258
% of Loans	0.10%	0.11%
90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 448	$ 585
% of Loans	0.18%	0.24%
Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 1,238	$ 1,504
% of Loans	0.50%	0.63%
Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 2,085	$ 1,635
% of Loans	0.84%	0.68%
Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 563	$ 166
% of Loans	0.23%	0.07%
Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		$ 1,719
% of Loans		0.72%
Total commercial
Financing Receivable, Past Due [Line Items]
Total Loans	$ 172,694	$ 160,602
Total commercial | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	171,627	159,825
Total commercial | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	69	155
Total commercial | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	47	36
Total commercial | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	36	85
Total commercial | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	152	276
Total commercial | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	915	501
Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	76,585	79,241
Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	73,766	74,994
Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	470	506
Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	204	222
Total consumer | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	412	500
Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,086	1,228
Total consumer | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,170	1,134
Total consumer | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	563	166
Total consumer | Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		1,719
Commercial and industrial [Member] | Total commercial
Financing Receivable, Past Due [Line Items]
Total Loans	137,187	125,337
Commercial and industrial [Member] | Total commercial | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	136,381	124,695
Commercial and industrial [Member] | Total commercial | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	56	102
Commercial and industrial [Member] | Total commercial | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	37	30
Commercial and industrial [Member] | Total commercial | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	36	85
Commercial and industrial [Member] | Total commercial | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	129	217
Commercial and industrial [Member] | Total commercial | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	677	425
Commercial Real Estate [Member] | Total commercial
Financing Receivable, Past Due [Line Items]
Total Loans	29,028	28,110
Commercial Real Estate [Member] | Total commercial | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	28,799	28,061
Commercial Real Estate [Member] | Total commercial | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6	4
Commercial Real Estate [Member] | Total commercial | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6	1
Commercial Real Estate [Member] | Total commercial | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	12	5
Commercial Real Estate [Member] | Total commercial | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	217	44
Equipment Lease Financing [Member] | Total commercial
Financing Receivable, Past Due [Line Items]
Total Loans	6,479	7,155
Equipment Lease Financing [Member] | Total commercial | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6,447	7,069
Equipment Lease Financing [Member] | Total commercial | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	7	49
Equipment Lease Financing [Member] | Total commercial | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4	5
Equipment Lease Financing [Member] | Total commercial | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	11	54
Equipment Lease Financing [Member] | Total commercial | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	21	32
Home Equity [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	24,539	25,085
Home Equity [Member] | Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	24,539	25,085
Home Equity [Member] | Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	23,774	23,791
Home Equity [Member] | Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	48	58
Home Equity [Member] | Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	22	24
Home Equity [Member] | Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	70	82
Home Equity [Member] | Total consumer | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	639	669
Home Equity [Member] | Total consumer | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	56
Home Equity [Member] | Total consumer | Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		543
Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	22,886	21,821
Residential Real Estate [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	851	584
Residential Real Estate [Member] | Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	22,886	21,821
Residential Real Estate [Member] | Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	21,503	19,640
Residential Real Estate [Member] | Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	188	140
Residential Real Estate [Member] | Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	80	69
Residential Real Estate [Member] | Total consumer | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	269	315
Residential Real Estate [Member] | Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	537	524
Residential Real Estate [Member] | Total consumer | Total Past Due [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	400	400
Residential Real Estate [Member] | Total consumer | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	339	315
Residential Real Estate [Member] | Total consumer | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	507	166
Residential Real Estate [Member] | Total consumer | Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		1,176
Automobile [Member] | Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	14,977	16,754
Automobile [Member] | Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	14,646	16,376
Automobile [Member] | Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	116	178
Automobile [Member] | Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	32	47
Automobile [Member] | Total consumer | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	12	18
Automobile [Member] | Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	160	243
Automobile [Member] | Total consumer | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	171	135
Credit Card [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		7,308
Credit Card [Member] | Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	6,303	7,308
Credit Card [Member] | Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6,153	7,133
Credit Card [Member] | Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	44	60
Credit Card [Member] | Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	33	37
Credit Card [Member] | Total consumer | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	60	67
Credit Card [Member] | Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	137	164
Credit Card [Member] | Total consumer | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	13	11
Education [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,051	3,336
Education [Member] | Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	3,051	3,336
Education [Member] | Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2,905	3,156
Education [Member] | Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	57	55
Education [Member] | Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	26	34
Education [Member] | Total consumer | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	63	91
Education [Member] | Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	146	180
Education [Member] | Total consumer | Total Past Due [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	100	200
Other Consumer [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4,829	4,937
Other Consumer [Member] | Total consumer
Financing Receivable, Past Due [Line Items]
Total Loans	4,829	4,937
Other Consumer [Member] | Total consumer | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4,785	4,898
Other Consumer [Member] | Total consumer | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	17	15
Other Consumer [Member] | Total consumer | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	11	11
Other Consumer [Member] | Total consumer | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	8	9
Other Consumer [Member] | Total consumer | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	36	35
Other Consumer [Member] | Total consumer | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 8	$ 4