LOANS RECEIVABLE AND REVENUE - Revenue by Product (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Revenue	$ 302,294	$ 297,264	$ 264,300	$ 277,939	$ 287,579	$ 269,482	$ 237,169	$ 250,843	$ 1,141,797	$ 1,045,073	$ 924,137
Consumer Portfolio Segment | Unsecured Installment
Revenue from External Customer [Line Items]
Revenue									530,730	523,282	454,758
Consumer Portfolio Segment | Secured Installment
Revenue from External Customer [Line Items]
Revenue									110,513	110,677	100,981
Consumer Portfolio Segment | Open-End
Revenue from External Customer [Line Items]
Revenue									245,256	141,963	73,496
Consumer Portfolio Segment | Single-Pay
Revenue from External Customer [Line Items]
Revenue									191,449	218,992	255,170
Ancillary
Revenue from External Customer [Line Items]
Revenue									63,849	50,159	39,732
Credit Services Organization Programs
Revenue from External Customer [Line Items]
Revenue									$ 289,300	$ 291,500	$ 265,200