Accounts payable and accrued expenses related parties current.

No definition available.

Name:	phat_AccountsPayableAndAccruedExpensesRelatedPartiesCurrent
Namespace Prefix:	phat_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Agreement extends period for termination.

+ References

No definition available.

+ Details

Name:	phat_AgreementExtendsPeriodForTermination
Namespace Prefix:	phat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

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

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_TypeOfArrangementAxis=phat_CommercialSupplyAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=phat_CommercialSupplyAgreementAndTemporaryServicesAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=phat_PCIPharmaServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=phat_ClinicalManufacturingServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=phat_TakedaPharmaceuticalCompanyLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions - Additional Information (Details) - USD ($)		12 Months Ended
	May 05, 2020	Dec. 31, 2022	Dec. 31, 2021
Commercial Supply Agreement
Related Party Transaction [Line Items]
Agreement extends period for termination	2 years
Commercial Supply and Temporary Services Agreement
Related Party Transaction [Line Items]
Minimum purchase obligation		$ 0
PCI Pharma Services \| Clinical Manufacturing Services
Related Party Transaction [Line Items]
Outstanding accounts payable and accrued expenses		1,100,000	$ 1,700,000
Expense related to services		700,000	3,200,000
Takeda \| Commercial Supply and Temporary Services Agreement
Related Party Transaction [Line Items]
Outstanding accounts payable and accrued expenses		1,400,000	900,000
Expense related to services		$ 1,400,000	$ 1,800,000