REVENUE - Revenue Stream (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 325,702	$ 227,375	$ 639,201	$ 492,966
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue	116,892	53,323	233,853	147,239
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	208,810	174,052	405,348	345,727
Perpetual license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue	12,596	9,057	18,048	12,716
Client Cloud
Disaggregation of Revenue [Line Items]
Revenue	183,078	116,488	370,148	280,440
Term license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue	104,296	44,266	215,805	134,523
Maintenance
Disaggregation of Revenue [Line Items]
Revenue	78,782	72,222	154,343	145,917
Maintenance | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	78,782	72,222	154,343	145,917
Pega Cloud
Disaggregation of Revenue [Line Items]
Revenue	73,293	48,838	141,151	92,304
Pega Cloud | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	73,293	48,838	141,151	92,304
Subscription
Disaggregation of Revenue [Line Items]
Revenue	256,371	165,326	511,299	372,744
Consulting
Disaggregation of Revenue [Line Items]
Revenue	56,735	52,992	109,854	107,506
Consulting | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	$ 56,735	$ 52,992	$ 109,854	$ 107,506