RESTRUCTURING - Schedule of Restructuring Liability (Details) - USD ($) $ in Thousands	12 Months Ended			31 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Restructuring Liability Rollforward [Line Items]
Stock-based compensation	$ 81,615	$ 64,821	$ 82,044
Restructuring Liability Rollforward [Roll Forward]
Restructuring reserve, beginning balance	1,119	4,121
Charges payable in cash	31	(136)
Cash payments	(436)	(2,777)
Foreign currency translation	(15)	(89)
Restructuring reserve, ending balance	699	1,119	4,121
Employee Severance and Benefit Costs
Restructuring Liability Rollforward [Line Items]
Restructuring Costs				$ 80,100
Restructuring Liability Rollforward [Roll Forward]
Restructuring reserve, beginning balance	1,119	3,817
Charges payable in cash	31	(353)
Cash payments	(436)	(2,256)
Foreign currency translation	(15)	(89)
Restructuring reserve, ending balance	699	1,119	3,817
Other Exit Costs
Restructuring Liability Rollforward [Roll Forward]
Restructuring reserve, beginning balance	0	304
Charges payable in cash	0	217
Cash payments	0	(521)
Foreign currency translation	0	0
Restructuring reserve, ending balance	0	0	304
Restructuring Charges
Restructuring Liability Rollforward [Line Items]
Stock-based compensation	$ 0	$ 0	$ 849