REVENUE - Schedule of Remaining Performance Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 1,265,367	$ 1,147,932
Revenue remaining performance obligation (in percent)	100.00%	100.00%
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
Revenue remaining performance obligation (in percent)		53.00%
Expected timing of satisfaction		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	$ 686,263	$ 283,762
Revenue remaining performance obligation (in percent)	54.00%	25.00%
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	$ 309,111	$ 145,232
Revenue remaining performance obligation (in percent)	24.00%	13.00%
Expected timing of satisfaction	1 year	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	$ 159,981	$ 101,247
Revenue remaining performance obligation (in percent)	13.00%	9.00%
Expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 110,012
Revenue remaining performance obligation (in percent)	9.00%
Expected timing of satisfaction
Maintenance
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 307,283	$ 286,880
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
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	202,610	55,141
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	58,610	24,496
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	28,585	16,198
Maintenance | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	17,478
Pega Cloud
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	842,759	739,638
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
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	391,324	213,304
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	239,787	115,416
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	121,778	82,807
Pega Cloud | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	89,870
Subscription license
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	63,965	77,020
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
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	48,427	4,113
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	4,356	1,420
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	8,518	1,734
Subscription license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	2,664
Perpetual license
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	7,263	7,571
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
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	4,567	4,505
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	2,696	2,252
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	0
Perpetual license | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	0
Consulting
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	44,097	36,823
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
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	39,335	6,699
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	3,662	1,648
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	1,100	$ 508
Consulting | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue remaining performance obligation	$ 0