LOANS RECEIVABLE AND REVENUE - Revenue by Product (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue from External Customer [Line Items]
Revenue	$ 261,758	$ 224,580
Consumer Portfolio Segment | Unsecured Installment
Revenue from External Customer [Line Items]
Revenue	132,946	109,431
Consumer Portfolio Segment | Secured Installment
Revenue from External Customer [Line Items]
Revenue	26,856	23,669
Consumer Portfolio Segment | Open-End
Revenue from External Customer [Line Items]
Revenue	27,223	17,907
Consumer Portfolio Segment | Single-Pay
Revenue from External Customer [Line Items]
Revenue	63,705	63,790
Ancillary
Revenue from External Customer [Line Items]
Revenue	$ 11,028	$ 9,783