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	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due
Portfolio loans and leases, net	$ 106,647	$ 106,329
Commercial
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	68,730	68,640
Past due	298	357
Portfolio loans and leases, net	69,028	68,997
90 days past due and still accruing	16	48
Commercial | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	174	171
Commercial | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	124	186
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	48,892	49,421
Past due	202	244
Portfolio loans and leases, net	49,094	49,665
90 days past due and still accruing	8	39
Commercial | Commercial and industrial loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	131	119
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	71	125
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	4,720	4,645
Past due	32	30
Portfolio loans and leases, net	4,752	4,675
90 days past due and still accruing	7	7
Commercial | Commercial mortgage owner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	11	7
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	21	23
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	5,683	5,860
Past due	46	67
Portfolio loans and leases, net	5,729	5,927
90 days past due and still accruing	0	1
Commercial | Commercial mortgage nonowner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	16	31
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	30	36
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	6,186	5,808
Past due	12	7
Portfolio loans and leases, net	6,198	5,815
90 days past due and still accruing	1	0
Commercial | Commercial construction loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	11	7
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	1	0
Commercial | Commercial leases
Financing Receivable, Recorded Investment, Past Due
Current loans and leases	3,249	2,906
Past due	6	9
Portfolio loans and leases, net	3,255	2,915
90 days past due and still accruing	0	1
Commercial | Commercial leases | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Past due	5	7
Commercial | Commercial leases | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Past due	$ 1	$ 2