Finance Receivables - Special Product (New Neighbor Guaranty program) - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Maximum future contingent payments	$ 20,900
Special Product [Member]
Accounts Notes And Loans Receivable [Line Items]
Delinquent assessments maximum due period purchases basis	48 months
New Neighbor Guaranty [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit losses	$ 0	$ 6,500