REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 205,592	$ 196,779	$ 418,138	$ 431,961
Percentage of sale revenue net	100.00%	100.00%	100.00%	100.00%
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	$ 44,274	$ 44,784	$ 107,538	$ 132,557
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	161,318	151,995	310,600	299,404
Perpetual license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	19,320	13,475	34,270	36,553
Term license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	24,954	31,309	73,268	96,004
Maintenance
Disaggregation of Revenue [Line Items]
Total revenue	69,329	65,906	137,035	130,431
Cloud | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	31,699	20,201	59,457	35,783
Consulting | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	60,290	65,888	114,108	133,190
Subscription
Disaggregation of Revenue [Line Items]
Total revenue	125,982	117,416	269,760	262,218
U.S.
Disaggregation of Revenue [Line Items]
Total revenue	119,682	110,349	223,673	224,334
Other Americas
Disaggregation of Revenue [Line Items]
Total revenue	8,873	9,627	37,702	27,342
United Kingdom (“U.K.”)
Disaggregation of Revenue [Line Items]
Total revenue	16,686	23,079	41,235	49,173
Europe (excluding U.K.), Middle East, and Africa
Disaggregation of Revenue [Line Items]
Total revenue	33,395	27,070	67,581	58,896
Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenue	$ 26,956	$ 26,654	$ 47,947	$ 72,216
Total Revenue | U.S.
Disaggregation of Revenue [Line Items]
Percentage of sale revenue net	59.00%	55.00%	54.00%	52.00%
Total Revenue | Other Americas
Disaggregation of Revenue [Line Items]
Percentage of sale revenue net	4.00%	5.00%	9.00%	6.00%
Total Revenue | United Kingdom (“U.K.”)
Disaggregation of Revenue [Line Items]
Percentage of sale revenue net	8.00%	12.00%	10.00%	11.00%
Total Revenue | Europe (excluding U.K.), Middle East, and Africa
Disaggregation of Revenue [Line Items]
Percentage of sale revenue net	16.00%	14.00%	16.00%	14.00%
Total Revenue | Asia-Pacific
Disaggregation of Revenue [Line Items]
Percentage of sale revenue net	13.00%	14.00%	11.00%	17.00%