Net Income Per Share - Stock Repurchase Program (Details) - USD ($) shares in Millions	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Stock repurchase program authorized amount		$ 265,000,000.0
Cumulative amount repurchased	$ 239,600,000
Cumulative number of shares repurchased	15.8

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