Loans (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Loans	$ 264,643	$ 239,843
Accrued Interest Receivable	$ 725
% of Loans	100.00%	100.00%
Financing receivable, deferred income	$ 1,300	$ 1,100
Collateral Dependent [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,100
Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 260,987	$ 234,819
% of Loans	98.62%	97.90%
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 688	$ 661
% of Loans	0.26%	0.28%
60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 261	$ 258
% of Loans	0.10%	0.11%
90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 534	$ 585
% of Loans	0.20%	0.24%
Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 1,483	$ 1,504
% of Loans	0.56%	0.63%
Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 1,644	$ 1,635
% of Loans	0.62%	0.68%
Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 529	$ 166
% of Loans	0.20%	0.07%
Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		$ 1,719
% of Loans		0.72%
Total commercial lending
Financing Receivable, Past Due [Line Items]
Total Loans	$ 184,736	$ 160,602
Accrued Interest Receivable	336
Total commercial lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	183,949	159,825
Total commercial lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	145	155
Total commercial lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	25	36
Total commercial lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	51	85
Total commercial lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	221	276
Total commercial lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	566	501
Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	79,907	79,241
Accrued Interest Receivable	389
Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	77,038	74,994
Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	543	506
Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	236	222
Total consumer lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	483	500
Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,262	1,228
Financing receivable, purchased with credit deterioration	100
Total consumer lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1,078	1,134
Total consumer lending | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	529	166
Total consumer lending | Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		1,719
Commercial Loan | Total commercial lending
Financing Receivable, Past Due [Line Items]
Total Loans	149,131	125,337
Accrued Interest Receivable	268
Commercial Loan | Total commercial lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	148,467	124,695
Commercial Loan | Total commercial lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	97	102
Commercial Loan | Total commercial lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	22	30
Commercial Loan | Total commercial lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	51	85
Commercial Loan | Total commercial lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	170	217
Commercial Loan | Total commercial lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	494	425
Commercial Real Estate [Member] | Total commercial lending
Financing Receivable, Past Due [Line Items]
Total Loans	28,544	28,110
Accrued Interest Receivable	68
Commercial Real Estate [Member] | Total commercial lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	28,495	28,061
Commercial Real Estate [Member] | Total commercial lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6	4
Commercial Real Estate [Member] | Total commercial lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	1	1
Commercial Real Estate [Member] | Total commercial lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	7	5
Commercial Real Estate [Member] | Total commercial lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	42	44
Equipment Lease Financing [Member] | Total commercial lending
Financing Receivable, Past Due [Line Items]
Total Loans	7,061	7,155
Equipment Lease Financing [Member] | Total commercial lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6,987	7,069
Equipment Lease Financing [Member] | Total commercial lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	42	49
Equipment Lease Financing [Member] | Total commercial lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	2	5
Equipment Lease Financing [Member] | Total commercial lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	44	54
Equipment Lease Financing [Member] | Total commercial lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	30	32
Home Equity [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	25,081	25,085
Home Equity [Member] | Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	25,081	25,085
Accrued Interest Receivable	118
Home Equity [Member] | Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	24,311	23,791
Home Equity [Member] | Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	65	58
Home Equity [Member] | Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	28	24
Home Equity [Member] | Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	93	82
Home Equity [Member] | Total consumer lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	617	669
Home Equity [Member] | Total consumer lending | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	60
Home Equity [Member] | Total consumer lending | 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	22,250	21,821
Residential Real Estate [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	580	584
Residential Real Estate [Member] | Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	22,250	21,821
Accrued Interest Receivable	59
Residential Real Estate [Member] | Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	20,934	19,640
Residential Real Estate [Member] | Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	173	140
Residential Real Estate [Member] | Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	82	69
Residential Real Estate [Member] | Total consumer lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	300	315
Residential Real Estate [Member] | Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	555	524
Residential Real Estate [Member] | Total consumer lending | 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 lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	292	315
Residential Real Estate [Member] | Total consumer lending | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	469	166
Residential Real Estate [Member] | Total consumer lending | Purchased Impaired Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		1,176
Automobile [Member] | Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	17,194	16,754
Accrued Interest Receivable	64
Automobile [Member] | Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	16,795	16,376
Automobile [Member] | Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	177	178
Automobile [Member] | Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	49	47
Automobile [Member] | Total consumer lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	19	18
Automobile [Member] | Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	245	243
Automobile [Member] | Total consumer lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	154	135
Credit Card [Member]
Financing Receivable, Past Due [Line Items]
Total Loans		7,308
Credit Card [Member] | Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	7,132	7,308
Credit Card [Member] | Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	6,956	7,133
Credit Card [Member] | Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	59	60
Credit Card [Member] | Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	37	37
Credit Card [Member] | Total consumer lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	70	67
Credit Card [Member] | Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	166	164
Credit Card [Member] | Total consumer lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	10	11
Education [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,247	3,336
Education [Member] | Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	3,247	3,336
Accrued Interest Receivable	134
Education [Member] | Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	3,081	3,156
Education [Member] | Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	52	55
Education [Member] | Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	30	34
Education [Member] | Total consumer lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	84	91
Education [Member] | Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	166	180
Education [Member] | Total consumer lending | Total Past Due [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	200	200
Other Consumer [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	5,003	4,937
Other Consumer [Member] | Total consumer lending
Financing Receivable, Past Due [Line Items]
Total Loans	5,003	4,937
Accrued Interest Receivable	14
Other Consumer [Member] | Total consumer lending | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	4,961	4,898
Other Consumer [Member] | Total consumer lending | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	17	15
Other Consumer [Member] | Total consumer lending | 60-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	10	11
Other Consumer [Member] | Total consumer lending | 90 Days or More Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	10	9
Other Consumer [Member] | Total consumer lending | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	37	35
Other Consumer [Member] | Total consumer lending | Nonperforming Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Loans	$ 5	$ 4