Summary of Significant Accounting Policies - Loans and Allowance for Credit Losses (Details)	9 Months Ended
	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for delinquency status of financing receivables	30 days
Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan origination fees and direct loan origination costs amortization period	12 months
Threshold period past due for write-off of trade accounts receivable	180 days
Credit Card | Privileges Revoked
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for write-off of trade accounts receivable	120 days
Credit Card | Notification of Death
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for write-off of trade accounts receivable	5 days
Credit Card | Chapter Seven Bankruptcy
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for write-off of trade accounts receivable	30 days
Consumer Banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for nonperforming status of financing receivables	90 days
Consumer Banking | Notification of Death
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for nonperforming status of financing receivables	60 days
Consumer Banking | Chapter Seven Bankruptcy
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for nonperforming status of financing receivables	60 days
Consumer Banking | Auto
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for nonperforming status of financing receivables	120 days
Consumer Banking | Small Business Banking Loans | Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period past due for nonperforming status of financing receivables	120 days
Consumer Banking | Other Consumer Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Threshold period following bankruptcy notice for write-off of financing receivable	40 days