REVENUE - Revenue Stream (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 216,703	$ 203,263	$ 634,841	$ 635,224
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	58,005	52,342	165,543	184,899
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	158,698	150,921	469,298	450,325
Perpetual license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	9,016	20,276	43,286	56,829
Term license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	48,989	32,066	122,257	128,070
Maintenance
Disaggregation of Revenue [Line Items]
Total revenue	70,371	66,017	207,406	196,448
Subscription
Disaggregation of Revenue [Line Items]
Total revenue	154,513	120,267	424,273	382,485
Cloud | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	35,153	22,184	94,610	57,967
Consulting | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	$ 53,174	$ 62,720	$ 167,282	$ 195,910