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	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	$ 105,700	$ 106,329
Commercial
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	67,020	68,997
90 Days Past Due and Still Accruing	6	48
Commercial | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	66,786	68,640
Commercial | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	234	357
Commercial | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	160	171
Commercial | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	74	186
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	47,564	49,665
90 Days Past Due and Still Accruing	2	39
Commercial | Commercial and industrial loans | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	47,398	49,421
Commercial | Commercial and industrial loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	166	244
Commercial | Commercial and industrial loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	111	119
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	55	125
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	4,757	4,675
90 Days Past Due and Still Accruing	4	7
Commercial | Commercial mortgage owner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	4,706	4,645
Commercial | Commercial mortgage owner-occupied loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	51	30
Commercial | Commercial mortgage owner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	35	7
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	16	23
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	5,590	5,927
90 Days Past Due and Still Accruing	0	1
Commercial | Commercial mortgage nonowner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	5,587	5,860
Commercial | Commercial mortgage nonowner-occupied loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3	67
Commercial | Commercial mortgage nonowner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1	31
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	2	36
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	5,871	5,815
90 Days Past Due and Still Accruing	0	0
Commercial | Commercial construction loans | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	5,871	5,808
Commercial | Commercial construction loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	0	7
Commercial | Commercial construction loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	0	7
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	0	0
Commercial | Commercial leases
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,238	2,915
90 Days Past Due and Still Accruing	0	1
Commercial | Commercial leases | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,224	2,906
Commercial | Commercial leases | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	14	9
Commercial | Commercial leases | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	13	7
Commercial | Commercial leases | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	$ 1	$ 2