Finance Receivables - Original Product - Schedule of Finance Receivables for Original Product (Detail) - Original Product [Member]	12 Months Ended
	Dec. 31, 2016 USD ($) Unit	Dec. 31, 2015 USD ($) Unit
Accounts Notes And Loans Receivable [Line Items]
Finance receivables outstanding	$ 1,036,000	$ 1,537,000
Number of active units with delinquent assessments | Unit	1,490	1,983
Amount of outstanding interest and late fees on active units	$ 18,000,000	$ 21,000,000
Funded During The Current Year [Member]
Accounts Notes And Loans Receivable [Line Items]
Finance receivables outstanding	80,000	94,000
1-2 Years Outstanding [Member]
Accounts Notes And Loans Receivable [Line Items]
Finance receivables outstanding	31,000	87,000
2-3 Years Outstanding [Member]
Accounts Notes And Loans Receivable [Line Items]
Finance receivables outstanding	37,000	193,000
3-4 Years Outstanding [Member]
Accounts Notes And Loans Receivable [Line Items]
Finance receivables outstanding	144,000	390,000
Greater Than 4 Years Outstanding [Member]
Accounts Notes And Loans Receivable [Line Items]
Finance receivables outstanding	$ 744,000	$ 773,000