- Financial Information for Polaris Acceptance Reflecting Effects of Securitization Facility (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Polaris Acceptance
Schedule of Investments [Line Items]
Revenues	$ 61,645	$ 66,414	$ 63,548
Interest and operating expenses	7,590	6,182	4,738
Net income	54,055	60,232	$ 58,810
Finance receivables, net	518,199	479,944
Other assets	96	200
Total Assets	518,295	480,144
Notes payable/(receivable)	(337,050)	(288,275)
Other liabilities	3,717	3,851
Partners' capital	177,528	188,018
Total Liabilities and Partners' Capital	$ 518,295	$ 480,144
Maximum
Schedule of Investments [Line Items]
Aggregate repurchase obligation	15.00%