SIGNIFICANT ACCOUNTING POLICIES - Schedule of effect of new accounting pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid and other current assets	$ 27,949	$ 15,516		$ 11,881
Deferred income tax assets	96,224	87,664		20,156
Accumulated deficit	$ (640,909)	$ (592,654)		$ (708,354)
Cumulative effect adjustment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid and other current assets			$ 1,903
Deferred income tax assets			(530)
Accumulated deficit			1,373
Adjusted balance
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid and other current assets			13,784
Deferred income tax assets			19,626
Accumulated deficit			$ (706,981)