Asset Quality - Financing Receivable Credit Quality Indicators (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 94,646	$ 89,552
Commercial Portfolio Segment Excluding PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	67,859	66,069
Commercial Portfolio Segment Excluding PCI Loans [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	65,624	63,904
Commercial Portfolio Segment Excluding PCI Loans [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,880	1,922
Commercial Portfolio Segment Excluding PCI Loans [Member] | Criticized Nonaccruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	355	243
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	48,247	45,692
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial, Financial and Agricultural [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	46,544	44,138
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial, Financial and Agricultural [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,439	1,402
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial, Financial and Agricultural [Member] | Criticized Nonaccruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	264	152
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	13,367	14,107
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Real Estate Loans [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	12,914	13,672
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Real Estate Loans [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	370	354
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Real Estate Loans [Member] | Criticized Nonaccruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	83	81
Commercial Portfolio Segment Excluding PCI Loans [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,557	1,664
Commercial Portfolio Segment Excluding PCI Loans [Member] | Construction Loans [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,524	1,537
Commercial Portfolio Segment Excluding PCI Loans [Member] | Construction Loans [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	31	125
Commercial Portfolio Segment Excluding PCI Loans [Member] | Construction Loans [Member] | Criticized Nonaccruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2	2
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	4,688	4,606
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	4,642	4,557
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	40	41
Commercial Portfolio Segment Excluding PCI Loans [Member] | Commercial Leases [Member] | Criticized Nonaccruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	6	8
Consumer Portfolio Segment Excluding PCI [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	26,341	22,908
Consumer Portfolio Segment Excluding PCI [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	15,212	12,511
Consumer Portfolio Segment Excluding PCI [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	8,028	7,433
Consumer Portfolio Segment Excluding PCI [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,347	2,316
Consumer Portfolio Segment Excluding PCI [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	754	648
Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	17,027	16,324
Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	10,583	9,794
Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	4,823	4,906
Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,360	1,411
Consumer Portfolio Segment Excluding PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	261	213
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	3,510	1,806
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,874	549
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,069	700
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	223	224
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Direct Loans [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	344	333
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,130	1,144
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	523	521
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	484	507
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	123	116
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Credit Card [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	4,674	3,634
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	2,232	1,647
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,652	1,320
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	641	565
Consumer Portfolio Segment Excluding PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	149	102
Commercial Portfolio Segment, PCI [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	173	241
Commercial Portfolio Segment, PCI [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	116	164
Commercial Portfolio Segment, PCI [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	57	77
Commercial Portfolio Segment, PCI [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	48	61
Commercial Portfolio Segment, PCI [Member] | Commercial, Financial and Agricultural [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	28	37
Commercial Portfolio Segment, PCI [Member] | Commercial, Financial and Agricultural [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	20	24
Commercial Portfolio Segment, PCI [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	124	178
Commercial Portfolio Segment, PCI [Member] | Commercial Real Estate Loans [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	87	125
Commercial Portfolio Segment, PCI [Member] | Commercial Real Estate Loans [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	37	53
Commercial Portfolio Segment, PCI [Member] | Construction Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1	2
Commercial Portfolio Segment, PCI [Member] | Construction Loans [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1	2
Commercial Portfolio Segment, PCI [Member] | Construction Loans [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Commercial Portfolio Segment, PCI [Member] | Commercial Leases [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Commercial Portfolio Segment, PCI [Member] | Commercial Leases [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Commercial Portfolio Segment, PCI [Member] | Commercial Leases [Member] | Criticized Accruing [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	273	334
Consumer Portfolio Segment, PCI [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	104	137
Consumer Portfolio Segment, PCI [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	92	96
Consumer Portfolio Segment, PCI [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	71	99
Consumer Portfolio Segment, PCI [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	6	2
Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	270	331
Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	103	137
Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	91	95
Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	70	97
Consumer Portfolio Segment, PCI [Member] | Residential Prime Financing Receivables [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	6	2
Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	3	3
Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1	0
Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1	1
Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1	2
Consumer Portfolio Segment, PCI [Member] | Consumer Direct Loans [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Credit Card [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, 750 and Above [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, 660 to 749 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, Less than 660 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	0	0
Consumer Portfolio Segment, PCI [Member] | Consumer Indirect Loans [Member] | FICO Score, No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 0	$ 0