Credit Quality and the Allowance for Loan and Lease Losses - Summary of Amortized Cost Basis of Modifications to Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	$ 86	$ 77
Term Extension
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	14	52
Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	10	11
Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	16	2
Term Extension and Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	1	0
Term Extension and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	38	11
Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	7	1
Commercial | Commercial and industrial loans
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	36	51
Commercial | Commercial and industrial loans | Term Extension
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	14	51
Commercial | Commercial and industrial loans | Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Commercial | Commercial and industrial loans | Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	13	0
Commercial | Commercial and industrial loans | Term Extension and Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	1	0
Commercial | Commercial and industrial loans | Term Extension and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	8	0
Commercial | Commercial and industrial loans | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Commercial | Commercial mortgage owner-occupied loans:
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	1
Commercial | Commercial mortgage owner-occupied loans: | Term Extension
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	1
Commercial | Commercial mortgage owner-occupied loans: | Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Commercial | Commercial mortgage owner-occupied loans: | Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Commercial | Commercial mortgage owner-occupied loans: | Term Extension and Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Commercial | Commercial mortgage owner-occupied loans: | Term Extension and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Commercial | Commercial mortgage owner-occupied loans: | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Residential Mortgage
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	38	14
Residential Mortgage | Term Extension
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Residential Mortgage | Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Residential Mortgage | Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	3	2
Residential Mortgage | Term Extension and Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Residential Mortgage | Term Extension and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	29	11
Residential Mortgage | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	6	1
Consumer | Home equity
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	3	1
Consumer | Home equity | Term Extension
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Home equity | Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	1	1
Consumer | Home equity | Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Home equity | Term Extension and Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Home equity | Term Extension and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	1	0
Consumer | Home equity | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	1	0
Consumer | Credit card
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	9	10
Consumer | Credit card | Term Extension
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	9	10
Consumer | Credit card | Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Credit card | Term Extension and Interest Rate Reduction
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Credit card | Term Extension and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	0	0
Consumer | Credit card | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Allowance for Credit Losses
Amortized cost basis of the modifications to borrowers experiencing financial difficulty	$ 0	$ 0