WARRANTY OBLIGATIONS - Narrative (Details) microinverter in Millions, $ in Millions	12 Months Ended			36 Months Ended	144 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 microinverter	Dec. 31, 2019 microinverter
Increased U.S. tariffs for products manufactured in China
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables	$ 5.5
Backwards compatibility cables
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		$ 0.9
Claim rates
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		2.1
Labor reimbursement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		0.2
Discount rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables		(1.5)
IQ Series
Product Liability Contingency [Line Items]
Number of units sold | microinverter				9.6
Percent of total sales	98.00%
Prior Generations
Product Liability Contingency [Line Items]
Number of units sold | microinverter					15.7
Second Generation
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables			$ (2.2)
Second Generation | Failure rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables			3.9
Second Generation | Labor reimbursement cost
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables			$ (1.9)
Second and Third Generations | Failure rate
Product Liability Contingency [Line Items]
Increase (decrease) in warranty expense due to changes in variables	$ 3.1	$ 3.3