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Data Type:	num:percentItemType
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Period Type:	duration

Represents the floor rate of the debt instrument

No definition available.

Name:	ptgx_DebtInstrumentFloorRate
Namespace Prefix:	ptgx_
Data Type:	num:percentItemType
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Represents the percentage of loan origination fee under the debt instrument.

No definition available.

Name:	ptgx_DebtInstrumentLoanOriginationFeePercentage
Namespace Prefix:	ptgx_
Data Type:	num:percentItemType
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Represents the period for which the company is required to pay interest-only payments on the debt instrument.

No definition available.

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Data Type:	xbrli:durationItemType
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Represents the period for which the company will pay principal and interest payments on the debt instrument.

No definition available.

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Data Type:	xbrli:durationItemType
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The percentage of prepayment premium under the debt instrument.

No definition available.

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Data Type:	num:percentItemType
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Represents the percentage on outstanding debt to be maintained as balance under cash and cash equivalents by the company.

No definition available.

Name:	ptgx_DebtInstrumentThresholdPercentageOnOutstandingDebtToBeMaintainedAsCashAndCashEquivalentsBalance
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Data Type:	num:percentItemType
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Represents the tranche installment amount under the debt instrument.

No definition available.

Name:	ptgx_DebtInstrumentTrancheInstallmentAmount
Namespace Prefix:	ptgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	num:percentItemType
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Name:	us-gaap_DebtInstrumentAxis=ptgx_TermLoanCreditAgreementMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_VariableRateAxis=us-gaap_PrimeRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=ptgx_DebtInstrumentRepaymentOnOrBeforeFirstAnniversaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementScenarioAxis=ptgx_DebtInstrumentRepaymentBetweenFirstAndSecondAnniversaryMember
Namespace Prefix:
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