Credit Quality and the Allowance for Loan and Lease Losses - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses
Mortgage loans in process of foreclosure amount	$ 101		$ 101		$ 107
Financing receivable, excluding accrued interest, modified in period, amount	$ 184	$ 171	$ 373	$ 484
Loan modification program, percentage of modifications to total portfolio	0.16%	0.14%	0.32%	0.40%
Loan modification program, loans excluded from modification program	$ 19	$ 6	$ 42	$ 24
Unfunded commitment amounts	80		80		$ 130
Commercial
Financing Receivable, Allowance for Credit Losses
Financing receivable, excluding accrued interest, modified in period, amount	$ 150	$ 124	$ 268	$ 355
Loan modification program, percentage of modifications to total portfolio	0.22%	0.17%	0.39%	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	$ 22	$ 31	$ 74	$ 89
Loan modification program, percentage of modifications to total portfolio	0.13%	0.18%	0.43%	0.51%
Modification program option, mortgage term			480 months
Modification program option, in-process modifications	$ 4	$ 7	$ 4	$ 7
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	$ 12	$ 16	$ 31	$ 40
Loan modification program, percentage of modifications to total portfolio	0.04%	0.06%	0.11%	0.14%
Consumer | Home equity
Financing Receivable, Allowance for Credit Losses
Financing receivable, excluding accrued interest, modified in period, amount	$ 4	$ 5	$ 11	$ 12
Loan modification program, percentage of modifications to total portfolio	0.10%	0.13%	0.27%	0.31%
Modification program option, mortgage term			360 months