Summary of Significant Accounting Policies and New Accounting Pronouncements - Charge-Off and Nonaccrual Policies and Practices (Details)	12 Months Ended
	Dec. 31, 2021
Commercial loans:
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of days contractually delinquent	3 months
Consumer loans: | Residential mortgages
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of days contractually delinquent	3 months
Period of consecutive payments	6 months
Delinquent threshold period	6 months
Update period	180 days
Valuation period from fair value determination date	90 days
Consumer loans: | Credit cards
Financing Receivable, Allowance for Credit Loss [Line Items]
Delinquent threshold period	6 months
Notification period	60 days
Delinquent threshold period involving a bankruptcy	180 days
Consumer loans: | Other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Delinquent threshold period	4 months