Loans and ACL - Aging Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable [Line Items]
Current	$ 141,531	$ 140,873
30-89 Days Past Due	1,052	1,077
90 Days Or More Past Due	548	636
Nonaccrual	570	736
Total	143,701	143,322
Commercial | Commercial and industrial
Financing Receivable [Line Items]
Current	58,852	57,326
30-89 Days Past Due	41	44
90 Days Or More Past Due	1	0
Nonaccrual	259	369
Total	59,153	57,739
Commercial | CRE
Financing Receivable [Line Items]
Current	21,209	19,699
30-89 Days Past Due	8	8
90 Days Or More Past Due	1	0
Nonaccrual	45	57
Total	21,263	19,764
Commercial | Lease financing
Financing Receivable [Line Items]
Current	1,906	1,669
30-89 Days Past Due	4	4
90 Days Or More Past Due	0	0
Nonaccrual	1	4
Total	1,911	1,677
Retail | Residential mortgage
Financing Receivable [Line Items]
Current	27,659	28,702
30-89 Days Past Due	472	525
90 Days Or More Past Due	465	522
Nonaccrual	129	172
Total	28,725	29,921
Retail | Direct
Financing Receivable [Line Items]
Current	11,756	11,963
30-89 Days Past Due	65	60
90 Days Or More Past Due	6	6
Nonaccrual	64	63
Total	11,891	12,092
Retail | Indirect
Financing Receivable [Line Items]
Current	16,745	18,110
30-89 Days Past Due	412	377
90 Days Or More Past Due	6	6
Nonaccrual	72	71
Total	17,235	18,564
Revolving credit
Financing Receivable [Line Items]
Current	2,837	2,620
30-89 Days Past Due	23	23
90 Days Or More Past Due	12	12
Nonaccrual	0	0
Total	2,872	2,655
PCI
Financing Receivable [Line Items]
Current	567	784
30-89 Days Past Due	27	36
90 Days Or More Past Due	57	90
Nonaccrual	0	0
Total	$ 651	$ 910