Loans and ACL - Aging Analysis of Loans and Leases (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable [Line Items]
Current	$ 144,647	$ 141,531
30-89 Days Past Due	1,075	1,052
90 Days Or More Past Due	431	548
Nonperforming	537	570
Total	146,690	143,701
Commercial | Commercial and industrial
Financing Receivable [Line Items]
Current	59,449	58,852
30-89 Days Past Due	35	41
90 Days Or More Past Due	0	1
Nonperforming	238	259
Total	59,722	59,153
Commercial | CRE
Financing Receivable [Line Items]
Current	21,416	21,209
30-89 Days Past Due	4	8
90 Days Or More Past Due	0	1
Nonperforming	46	45
Total	21,466	21,263
Commercial | Lease financing
Financing Receivable [Line Items]
Current	2,021	1,906
30-89 Days Past Due	1	4
90 Days Or More Past Due	0	0
Nonperforming	6	1
Total	2,028	1,911
Retail | Residential mortgage
Financing Receivable [Line Items]
Current	29,824	27,659
30-89 Days Past Due	510	472
90 Days Or More Past Due	367	465
Nonperforming	120	129
Total	30,821	28,725
Retail | Direct
Financing Receivable [Line Items]
Current	11,498	11,756
30-89 Days Past Due	59	65
90 Days Or More Past Due	6	6
Nonperforming	55	64
Total	11,618	11,891
Retail | Indirect
Financing Receivable [Line Items]
Current	16,972	16,745
30-89 Days Past Due	418	412
90 Days Or More Past Due	6	6
Nonperforming	72	72
Total	17,468	17,235
Revolving credit
Financing Receivable [Line Items]
Current	3,031	2,837
30-89 Days Past Due	27	23
90 Days Or More Past Due	12	12
Nonperforming	0	0
Total	3,070	2,872
PCI
Financing Receivable [Line Items]
Current	436	567
30-89 Days Past Due	21	27
90 Days Or More Past Due	40	57
Nonperforming	0	0
Total	$ 497	$ 651