Revenue - Services Revenue (Details) - Services	9 Months Ended
Sep. 30, 2018
Minimum
Disaggregation of Revenue [Line Items]
Notice period to cancel or terminate contract	10 days
Maximum
Disaggregation of Revenue [Line Items]
Notice period to cancel or terminate contract	30 days

Period of time for the client or the Company to cancel or terminate the contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	prft_NoticePeriodToCancelOrTerminateContract
Namespace Prefix:	prft_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration