REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenue		$ 256,357	$ 203,263	$ 196,779	$ 235,182	$ 254,605	$ 190,957	$ 186,596	$ 256,309	$ 891,581	[1]	$ 888,467	[1]	$ 762,229	[1]
Perpetual license
Disaggregation of Revenue [Line Items]
Total revenue										109,863		132,883		145,053
Term license
Disaggregation of Revenue [Line Items]
Total revenue										178,256		206,411		152,231
Maintenance
Disaggregation of Revenue [Line Items]
Total revenue	[1]									263,875		242,320		218,635
Subscription
Disaggregation of Revenue [Line Items]
Total revenue										524,758		499,828		411,513
Cloud
Disaggregation of Revenue [Line Items]
Total revenue										82,627		51,097		40,647
Consulting
Disaggregation of Revenue [Line Items]
Total revenue										256,960		255,756		205,663
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue										288,119		339,294		297,284
Revenue recognized at a point in time | Perpetual license
Disaggregation of Revenue [Line Items]
Total revenue										109,863		132,883		145,053
Revenue recognized at a point in time | Term license
Disaggregation of Revenue [Line Items]
Total revenue										178,256		206,411		152,231
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue										603,462		549,173		464,945
Revenue recognized over time | Maintenance
Disaggregation of Revenue [Line Items]
Total revenue										263,875		242,320		218,635
Revenue recognized over time | Cloud
Disaggregation of Revenue [Line Items]
Total revenue										82,627		51,097		40,647
Revenue recognized over time | Consulting
Disaggregation of Revenue [Line Items]
Total revenue										$ 256,960		$ 255,756		$ 205,663

[1] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.