REVISION OF PRIOR PERIOD FINANCIAL STATEMENTS - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued expenses	$ 183,382	$ 134,635
Accumulated deficit	(1,015,201)	(547,540)
As reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued expenses	177,079	129,537
Accumulated deficit	(1,008,898)	(542,442)
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued expenses	6,303	5,098
Accumulated deficit	$ (6,303)	$ (5,098)	$ (800)