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Share-Based Compensation - Schedule of Fair Value of Stock Option Award Granted Estimated on Date of Grant Using the Black-Scholes-Merton Option Pricing Model (Parenthetical) (Detail) | 12 Months Ended
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Dec. 31, 2020 shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
Awarded, Options | 0

X
- Definition Net number of share options (or share units) awarded during the period. + References No definition available. + Details
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Namespace Prefix: | prdo_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration