Credit Quality and the Allowance for Loan and Lease Losses - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses
Mortgage loans in process of foreclosure amount	$ 93		$ 93		$ 107
Financing receivable, excluding accrued interest, modified in period, amount	$ 183	$ 331	$ 300	$ 444
Loan modification program, percentage of modifications to total portfolio	0.16%	0.27%	0.26%	0.36%
Loan modification program, loans excluded from modification program	$ 21	$ 9	$ 30	$ 20
Unfunded commitment amounts	88		88		$ 130
Commercial
Financing Receivable, Allowance for Credit Losses
Financing receivable, excluding accrued interest, modified in period, amount	$ 144	$ 282	$ 226	$ 358
Loan modification program, percentage of modifications to total portfolio	0.20%	0.37%	0.31%	0.47%
Commercial | Minimum
Financing Receivable, Allowance for Credit Losses
Term extension period			3 months
Commercial | Maximum
Financing Receivable, Allowance for Credit Losses
Term extension period			12 months
Residential Mortgage
Financing Receivable, Allowance for Credit Losses
Financing receivable, excluding accrued interest, modified in period, amount	$ 29	$ 36	$ 53	$ 59
Loan modification program, percentage of modifications to total portfolio	0.17%	0.21%	0.31%	0.34%
Modification program option, mortgage term			480 months
Modification program option, in-process modifications	$ 3	$ 17	$ 3	$ 17
Residential Mortgage | Minimum
Financing Receivable, Allowance for Credit Losses
Modification program option, trial period			3 months
Modification program option, mortgage interest payment deferral, term			6 months
Residential Mortgage | Maximum
Financing Receivable, Allowance for Credit Losses
Modification program option, trial period			4 months
Modification program option, mortgage interest payment deferral, term			12 months
Consumer
Financing Receivable, Allowance for Credit Losses
Financing receivable, excluding accrued interest, modified in period, amount	$ 10	$ 13	$ 21	$ 27
Loan modification program, percentage of modifications to total portfolio	0.04%	0.05%	0.08%	0.10%
Consumer | Home equity
Financing Receivable, Allowance for Credit Losses
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 3	$ 7	$ 7
Loan modification program, percentage of modifications to total portfolio	0.08%	0.08%	0.18%	0.18%
Modification program option, mortgage term			360 months