Name:	ptgx_CashEquivalentsAndAvailableForSaleSecuritiesLineItems
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Data Type:	xbrli:stringItemType
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This item represents the cost of debt and equity securities, including cash equivalents which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

No definition available.

Name:	ptgx_CashEquivalentsAndMarketableSecuritiesAmortizedCost
Namespace Prefix:	ptgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The aggregate fair value of amount of investment in debt and equity securities and cash equivalents categorized neither as held-to-maturity nor trading.

No definition available.

Name:	ptgx_CashEquivalentsAndMarketableSecuritiesFairValue
Namespace Prefix:	ptgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as cash equivalents and marketable securities.

No definition available.

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

Amount of unrealized loss before deducting unrealized gain on investments in cash equivalents and marketable securities.

No definition available.

Name:	ptgx_CashEquivalentsAndMarketableSecuritiesGrossUnrealizedLoss
Namespace Prefix:	ptgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember
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