Allowance for Credit Losses - Amortized Cost Basis of Financing Receivables that Subsequently Defaulted (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified Loans	$ 9,467	$ 12,660
Payment Default	9,289	12,463
Combination - Interest Rate Reduction and Term Extension
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified Loans	8,500	11,400
Interest Rate Reduction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified Loans	1,000	1,200
Private Education Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified Loans	9,467	12,660
Payment Default	$ 9,289	$ 12,463