Name:	ptgx_CashEquivalentsAndMarketableSecuritiesFairValue
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represents the maximum period of current contractual maturities.

No definition available.

Name:	ptgx_CurrentContractualMaturitiesMaximumPeriod
Namespace Prefix:	ptgx_
Data Type:	xbrli:durationItemType
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Represents the maximum period of contractual maturities.

No definition available.

Name:	ptgx_NoncurrentContractualMaturitiesMaximumPeriod
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Data Type:	xbrli:durationItemType
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Period Type:	duration

Represents the minimum period of noncurrent contractual maturities.

No definition available.

Name:	ptgx_NoncurrentContractualMaturitiesMinimumPeriod
Namespace Prefix:	ptgx_
Data Type:	xbrli:durationItemType
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Period Type:	duration

- References

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract
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Data Type:	xbrli:stringItemType
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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Name:	us-gaap_CashEquivalentsAtCarryingValue
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Data Type:	xbrli:monetaryItemType
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- References

No definition available.

Name:	us-gaap_InvestmentsAndCashAbstract
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Data Type:	xbrli:stringItemType
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Amount of investment in marketable security, classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Name:	us-gaap_MarketableSecuritiesCurrent
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Data Type:	xbrli:monetaryItemType
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Amount of investment in marketable security, classified as noncurrent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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

Amount of realized gain (loss) on investment in marketable security, excluding other-than-temporary impairment (OTTI).

No definition available.