Credit Quality and the Allowance for Loan and Lease Losses - Summary of Recorded Investment in Portfolio Loans and Leases by Age and Class (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment, Past Due
Portfolio loans and leases, net	$ 106,329	$ 108,356
Residential mortgage loans
Financing Receivable, Recorded Investment, Past Due
Portfolio loans and leases at fair value	161	183
Commercial
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	68,640	69,657
Past due	357	301
Portfolio loans and leases, net	68,997	69,958
90 days past due and still accruing	48	26
Commercial | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	171	154
Commercial | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	186	147
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	49,421	50,305
Past due	244	237
Portfolio loans and leases, net	49,665	50,542
90 days past due and still accruing	39	11
Commercial | Commercial and industrial loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	119	133
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	125	104
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	4,645	4,853
Past due	30	27
Portfolio loans and leases, net	4,675	4,880
90 days past due and still accruing	7	9
Commercial | Commercial mortgage owner-occupied loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	7	4
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	23	23
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	5,860	6,072
Past due	67	11
Portfolio loans and leases, net	5,927	6,083
90 days past due and still accruing	1	6
Commercial | Commercial mortgage nonowner-occupied loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	31	5
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	36	6
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	5,808	5,089
Past due	7	1
Portfolio loans and leases, net	5,815	5,090
90 days past due and still accruing	0	0
Commercial | Commercial construction loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	7	1
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	0	0
Commercial | Commercial leases
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	2,906	3,338
Past due	9	25
Portfolio loans and leases, net	2,915	3,363
90 days past due and still accruing	1	0
Commercial | Commercial leases | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	7	11
Commercial | Commercial leases | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	2	14
Residential Mortgage Loans
Financing Receivable, Recorded Investment, Past Due
Portfolio loans and leases at fair value	161	183
Residential Mortgage Loans | Federal Housing Administration Loan
Financing Receivable, Recorded Investment, Past Due
Losses due to claim denials and curtailments	3	4
Residential Mortgage Loans | 30-89 Days | Federal Housing Administration Loan
Financing Receivable, Recorded Investment, Past Due
Past due	103	94
Residential Mortgage Loans | 90 Days or More | Federal Housing Administration Loan
Financing Receivable, Recorded Investment, Past Due
Past due	$ 242	261
Residential Mortgage Loans | Residential mortgage loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		16,372
Past due		169
Portfolio loans and leases, net		16,541
90 days past due and still accruing		50
Residential Mortgage Loans | Residential mortgage loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		27
Residential Mortgage Loans | Residential mortgage loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		142
Consumer | Home equity
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		5,965
Past due		118
Portfolio loans and leases, net		6,083
90 days past due and still accruing		1
Consumer | Home equity | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		61
Consumer | Home equity | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		57
Consumer | Indirect secured consumer loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		11,389
Past due		149
Portfolio loans and leases, net		11,538
90 days past due and still accruing		10
Consumer | Indirect secured consumer loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		132
Consumer | Indirect secured consumer loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		17
Consumer | Credit card
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		2,434
Past due		98
Portfolio loans and leases, net		2,532
90 days past due and still accruing		42
Consumer | Credit card | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		50
Consumer | Credit card | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		48
Consumer | Other consumer loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		2,702
Past due		21
Portfolio loans and leases, net		2,723
90 days past due and still accruing		1
Consumer | Other consumer loans | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		18
Consumer | Other consumer loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		3
Residential Mortgage and Consumer
Financing Receivable, Recorded Investment, Past Due
Current loans and leases		38,862
Past due		555
Portfolio loans and leases, net		39,417
90 days past due and still accruing		104
Residential Mortgage and Consumer | 30-89 Days
Financing Receivable, Recorded Investment, Past Due
Past due		288
Residential Mortgage and Consumer | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due		$ 267