REVENUE RECOGNITION - Liability for Customer Credits Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Movement in Customer Refundable Fees [Roll Forward]
Customer Credits, Credits Issued	$ 115,031	$ 126,874
Customer Credits, Credits Redeemed	(102,682)	(112,161)
Customer Credits, Breakage Revenue Recognized	(13,699)	(18,802)
Customer Credits, Foreign Currency Translation	(4)	(207)
Customer credits	$ 13,764	$ 15,118	$ 19,414