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Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details) | Mar. 31, 2020 Institution
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Summary of Significant Accounting Policies |
Number of financial institutions at which cash is held | 2

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- Definition The number of financial institutions that hold the entity's cash. + References No definition available. + Details
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Namespace Prefix: | ptgx_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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