REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 276,542	$ 216,703	$ 205,592	$ 212,546	$ 256,357	$ 203,263	$ 196,779	$ 235,182	$ 911,383	$ 891,581	$ 888,467
Perpetual license
Disaggregation of Revenue [Line Items]
Revenue									80,015	109,863	132,883
Term license
Disaggregation of Revenue [Line Items]
Revenue									199,433	178,256	206,411
Maintenance
Disaggregation of Revenue [Line Items]
Revenue									280,580	263,875	242,320
Subscription
Disaggregation of Revenue [Line Items]
Revenue									613,759	524,758	499,828
Cloud
Disaggregation of Revenue [Line Items]
Revenue									133,746	82,627	51,097
Consulting
Disaggregation of Revenue [Line Items]
Revenue									217,609	256,960	255,756
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue									279,448	288,119	339,294
Revenue recognized at a point in time | Perpetual license
Disaggregation of Revenue [Line Items]
Revenue									80,015	109,863	132,883
Revenue recognized at a point in time | Term license
Disaggregation of Revenue [Line Items]
Revenue									199,433	178,256	206,411
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue									631,935	603,462	549,173
Revenue recognized over time | Maintenance
Disaggregation of Revenue [Line Items]
Revenue									280,580	263,875	242,320
Revenue recognized over time | Cloud
Disaggregation of Revenue [Line Items]
Revenue									133,746	82,627	51,097
Revenue recognized over time | Consulting
Disaggregation of Revenue [Line Items]
Revenue									$ 217,609	$ 256,960	$ 255,756