REVENUE - Revenue Stream (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 225,951	$ 216,703	$ 718,917	$ 634,841
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue	39,784	58,005	187,023	165,543
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	186,167	158,698	531,894	469,298
Perpetual license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue	3,852	9,016	16,568	43,286
Term license | Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenue	35,932	48,989	170,455	122,257
Maintenance
Disaggregation of Revenue [Line Items]
Revenue	74,670	70,371	220,587	207,406
Maintenance | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	74,670	70,371	220,587	207,406
Pega Cloud
Disaggregation of Revenue [Line Items]
Revenue	54,776	35,153	147,080	94,610
Pega Cloud | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	54,776	35,153	147,080	94,610
Subscription
Disaggregation of Revenue [Line Items]
Revenue	165,378	154,513	538,122	424,273
Consulting
Disaggregation of Revenue [Line Items]
Revenue	56,721	53,174	164,227	167,282
Consulting | Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenue	$ 56,721	$ 53,174	$ 164,227	$ 167,282