FAIR VALUE MEASUREMENTS - Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3 (Details) - Recurring - Level 3	Dec. 31, 2018	Dec. 31, 2017
Measurement Input, Profit Element and Risk Premium | Warranty obligations for microinverters sold since January 1, 2014
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations for microinverters sold since January 1, 2014	0.1625	0.17
Measurement Input, Entity Credit Risk | Warranty obligations for microinverters sold since January 1, 2014
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations for microinverters sold since January 1, 2014	0.1875	0.17
Measurement Input, Counterparty Credit Risk | Third party option to purchase receivables at a discount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Third party option to purchase receivables at a discount		0.04