FAIR VALUE MEASUREMENTS - Schedule of Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - Level 3 - Total warranty obligations measured at fair value - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warranty obligations, current	$ 6,794	$ 4,288
Warranty obligations, non-current	13,012	7,469
Obligations measured at fair value	$ 19,806	$ 11,757	$ 9,791	$ 10,332