Net Income per Share - Additional Information (Details) shares in Millions	Sep. 30, 2020 USD ($) shares
Earnings Per Share [Abstract]
Shares authorized to repurchase	$ 265,000,000.0
Cumulative amount repurchased	$ 231,200,000
Cumulative number of shares repurchased (in shares) \| shares	15.6

The cumulative number of shares of stock repurchased under the plan.

No definition available.

Name:	prft_StockRepurchaseProgramCumulativeAmountRepurchasedShares
Namespace Prefix:	prft_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant