VEHICLE SERVICE AGREEMENT LIABILITY - Components of deferred services fees and accrued expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Product Warranty Liability [Line Items]
Deferred service fees	$ 56,219	$ 56,252
Accrued expenses and other liabilities	27,266	26,993
Vehicle service agreement fees
Product Warranty Liability [Line Items]
Deferred service fees	50,946	51,226
Accrued expenses and other liabilities	526	497
Balance at end of period, net	$ 51,472	$ 51,723	$ 55,983	$ 43,734