RESTRUCTURING CHARGES - Narrative (Details) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) employee	Mar. 31, 2017 employee	Jun. 30, 2019 USD ($) employee	Dec. 31, 2018 USD ($) employee	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 13,895	$ 3,363			$ 17,514	$ 3,821
Q4 FY2017 Plan
Restructuring Cost and Reserve [Line Items]
Number of employees terminated | employee			41
Q4 FY2017 Plan | Employee-Related
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 0				700	$ 1,900
Q4 FY2017 Plan | Facility-Related
Restructuring Cost and Reserve [Line Items]
Restructuring charges							$ 400
Q3 FY 2018 Plan
Restructuring Cost and Reserve [Line Items]
Number of employees terminated | employee		61
Restructuring charges	0				$ 1,700
Q3 FY 2018 Plan | Employee-Related
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 3,600				$ 3,600
VSP
Restructuring Cost and Reserve [Line Items]
Number of employees terminated | employee					147
Restructuring charges	$ 13,800				$ 16,100
VSP | Scenario, Forecast
Restructuring Cost and Reserve [Line Items]
Number of employees terminated | employee				13
Restructuring charges				$ 1,800