REVENUE - Performance Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 1,147,932	$ 1,034,026
Revenue remaining performance obligation (in percent)	100.00%	100.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation		$ 577,650
Revenue remaining performance obligation (in percent)		56.00%
Expected timing of satisfaction		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 617,691	$ 261,071
Revenue remaining performance obligation (in percent)	53.00%	25.00%
Expected timing of satisfaction	1 year	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 283,762	$ 127,188
Revenue remaining performance obligation (in percent)	25.00%	12.00%
Expected timing of satisfaction	1 year	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 145,232	$ 68,117
Revenue remaining performance obligation (in percent)	13.00%	7.00%
Expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 101,247
Revenue remaining performance obligation (in percent)	9.00%
Expected timing of satisfaction
Maintenance
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 286,880	$ 327,696
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation		196,667
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	191,045	59,360
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	55,141	37,734
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	24,496	33,935
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	16,198
Pega Cloud
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	739,638	571,461
Pega Cloud | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation		284,359
Pega Cloud | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	328,111	177,214
Pega Cloud | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	213,304	79,775
Pega Cloud | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	115,416	30,113
Pega Cloud | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	82,807
Subscription license
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	77,020	66,802
Subscription license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation		49,265
Subscription license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	69,753	16,872
Subscription license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	4,113	420
Subscription license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	1,420	245
Subscription license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	1,734
Perpetual license
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	7,571	22,971
Perpetual license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation		15,686
Perpetual license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	814	1,064
Perpetual license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	4,505	4,094
Perpetual license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	2,252	2,127
Perpetual license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	0
Consulting
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	36,823	45,096
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation		31,673
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	27,968	6,561
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	6,699	5,165
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	1,648	$ 1,697
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 508