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		Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	[1]	$ 116,668	$ 117,234
Commercial
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		71,130	72,746
90 Days Past Due and Still Accruing		14	8
Commercial | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		70,971	72,547
Commercial | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		159	199
Commercial | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		63	93
Commercial | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		96	106
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		50,916	53,270
90 Days Past Due and Still Accruing		10	8
Commercial | Commercial and industrial loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		50,785	53,107
Commercial | Commercial and industrial loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		131	163
Commercial | Commercial and industrial loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		44	61
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		87	102
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5,427	5,200
90 Days Past Due and Still Accruing		1	0
Commercial | Commercial mortgage owner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5,418	5,196
Commercial | Commercial mortgage owner-occupied loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		9	4
Commercial | Commercial mortgage owner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		6	1
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		3	3
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5,967	6,076
90 Days Past Due and Still Accruing		2	0
Commercial | Commercial mortgage nonowner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5,961	6,061
Commercial | Commercial mortgage nonowner-occupied loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		6	15
Commercial | Commercial mortgage nonowner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		1	14
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5	1
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5,947	5,621
90 Days Past Due and Still Accruing		0	0
Commercial | Commercial construction loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		5,947	5,621
Commercial | Commercial construction loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		0	0
Commercial | Commercial construction loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		0	0
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		0	0
Commercial | Commercial leases
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		2,873	2,579
90 Days Past Due and Still Accruing		1	0
Commercial | Commercial leases | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		2,860	2,562
Commercial | Commercial leases | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		13	17
Commercial | Commercial leases | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		12	17
Commercial | Commercial leases | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases		$ 1	$ 0

[1] Includes $50 and $55 of other short-term investments, $1,131 and $1,573 of portfolio loans and leases, $(21) and $(28) of ALLL, $8 and $10 of other assets, $13 and $14 of other liabilities and $1,008 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2024 and December 31, 2023, respectively. For further information, refer to Note 12.