Deferred Contract Costs - Additional Information (Detail)	9 Months Ended
Sep. 30, 2018
Amortized period	5 years

Average amortization period for deferred contract costs.

No definition available.

Name:	pega_AmortizationPeriodForDeferredContactCosts
Namespace Prefix:	pega_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration