WARRANTY OBLIGATIONS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Product Warranty Liability [Line Items]
Additional warranty expense	$ 7,655	$ 1,677
Field Performance Data And Diagnostic Root-Cause Failure Analysis
Product Warranty Liability [Line Items]
Additional warranty expense	6,300	1,500
Unit Costs For Prior Generation Microinverter Replacement Driven By Tariffs
Product Warranty Liability [Line Items]
Additional warranty expense	$ 1,300	$ 200

Amount of increase (decrease) in the standard and extended product warranty accrual from changes in estimates attributable to preexisting product warranties.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph ((c)(4))
-URI http://asc.fasb.org/extlink&oid=68068213&loc=d3e12565-110249

Name:	us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration