Loans and ACL - Aging Analysis of Loans and Leases (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable [Line Items]
Current	$ 141,111	$ 141,531
30-89 Days Past Due	814	1,052
90 Days Or More Past Due	490	548
Nonaccrual	602	570
Total	143,017	143,701
Commercial | Commercial and industrial
Financing Receivable [Line Items]
Current	58,844	58,852
30-89 Days Past Due	31	41
90 Days Or More Past Due	0	1
Nonaccrual	257	259
Total	59,132	59,153
Commercial | CRE
Financing Receivable [Line Items]
Current	21,420	21,209
30-89 Days Past Due	10	8
90 Days Or More Past Due	0	1
Nonaccrual	67	45
Total	21,497	21,263
Commercial | Lease financing
Financing Receivable [Line Items]
Current	1,872	1,906
30-89 Days Past Due	1	4
90 Days Or More Past Due	0	0
Nonaccrual	13	1
Total	1,886	1,911
Retail | Residential mortgage
Financing Receivable [Line Items]
Current	27,845	27,659
30-89 Days Past Due	400	472
90 Days Or More Past Due	420	465
Nonaccrual	127	129
Total	28,792	28,725
Retail | Direct
Financing Receivable [Line Items]
Current	11,550	11,756
30-89 Days Past Due	55	65
90 Days Or More Past Due	6	6
Nonaccrual	64	64
Total	11,675	11,891
Retail | Indirect
Financing Receivable [Line Items]
Current	16,329	16,745
30-89 Days Past Due	272	412
90 Days Or More Past Due	5	6
Nonaccrual	74	72
Total	16,680	17,235
Revolving credit
Financing Receivable [Line Items]
Current	2,734	2,837
30-89 Days Past Due	21	23
90 Days Or More Past Due	11	12
Nonaccrual	0	0
Total	2,766	2,872
PCI
Financing Receivable [Line Items]
Current	517	567
30-89 Days Past Due	24	27
90 Days Or More Past Due	48	57
Nonaccrual	0	0
Total	$ 589	$ 651