Aggregate purchase price.

No definition available.

Name:	pstv_AggregatePurchasePrice
Namespace Prefix:	pstv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Class of warrant or right expiration period.

+ References

No definition available.

+ Details

Name:	pstv_ClassOfWarrantOrRightExpirationPeriod
Namespace Prefix:	pstv_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum beneficial ownership percentage.

+ References

No definition available.

+ Details

Name:	pstv_MaximumBeneficialOwnershipPercentage
Namespace Prefix:	pstv_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum beneficial ownership percentage by election of holder.

+ References

No definition available.

+ Details

Name:	pstv_MaximumBeneficialOwnershipPercentageByElectionOfHolder
Namespace Prefix:	pstv_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

purchase price of share.

+ References

No definition available.

+ Details

Name:	pstv_PurchasePriceOfShare
Namespace Prefix:	pstv_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-3

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Face amount or stated value per share of common stock.

+ References

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(a)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 14
-Subparagraph (a)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-14

+ Details

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

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-SubTopic 10
-Topic 505
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(4)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481674/830-30-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 855
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483399/855-10-50-2

+ Details

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

- Definition

Per share decrease in exercise price of warrant. Excludes change due to standard antidilution provision.

+ References

+ Details

Name:	us-gaap_WarrantExercisePriceDecrease
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=pstv_MayTwoThousandTwentyFourPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=pstv_SeriesAWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=pstv_FebruaryTwoThousandTwentyFiveSecuritiesPurchaseAndExchangeAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=pstv_SPEAWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=pstv_MarchTwoThousandTwentyFivePrivatePlacementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis=pstv_ExchangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis=pstv_NewCapitalSubscriptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=pstv_SeriesBWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=pstv_SecuritiesPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_PrivatePlacementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=pstv_PrefundedWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events - Additional Information (Details) - USD ($)					1 Months Ended	12 Months Ended
	Mar. 07, 2025	Mar. 04, 2025	Feb. 13, 2025	May 08, 2024	Mar. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Subsequent Event [Line Items]
Common stock, par value (in dollars per share)						$ 0.001	$ 0.001
Common Stock [Member]
Subsequent Event [Line Items]
Issue and sale of share						1,439,988	2,230,493
May 2024 Purchase Agreement
Subsequent Event [Line Items]
Aggregate principal amount				$ 3,188,922
May 2024 Purchase Agreement \| Common Stock [Member] \| Series A Warrant [Member]
Subsequent Event [Line Items]
Number of shares issued				3,591,532
Subsequent Event [Member] \| February 2025 SPEA Agreements
Subsequent Event [Line Items]
Common stock, par value (in dollars per share)			$ 0.001
Warrant exercise price (in dollars per share)			1.12
Purchase price of share			$ 0.125
Maturity date			Feb. 13, 2026
Interest Rate			10.00%
Aggregate purchase price			$ 3,700,000
Reduction of exercise price of Warrants					$ 0.125
Subsequent Event [Member] \| February 2025 SPEA Agreements \| SPEA Warrants [Member]
Subsequent Event [Line Items]
Number of securities called by warrant or right			3,002,009
Aggregate purchase price			$ 4,250,000
Subsequent Event [Member] \| February 2025 SPEA Agreements \| Common Stock [Member]
Subsequent Event [Line Items]
Aggregate principal amount			$ 3,362,251
Number of securities called by warrant or right			3,002,009
Subsequent Event [Member] \| March 2025 Private Placement
Subsequent Event [Line Items]
Aggregate principal amount			$ 3,362,251
Subsequent Event [Member] \| March 2025 Private Placement \| Exchange [Member]
Subsequent Event [Line Items]
Aggregate principal amount		$ 3,200,000
Subsequent Event [Member] \| March 2025 Private Placement \| Series A Warrant [Member] \| New Capital Subscriptions [Member]
Subsequent Event [Line Items]
Number of shares issued		22,727,270
Subsequent Event [Member] \| March 2025 Private Placement \| Series A Warrant [Member] \| Exchange [Member]
Subsequent Event [Line Items]
Number of shares issued		5,314,870
Subsequent Event [Member] \| March 2025 Private Placement \| Series B Warrant [Member] \| New Capital Subscriptions [Member]
Subsequent Event [Line Items]
Number of shares issued		22,727,270
Subsequent Event [Member] \| March 2025 Private Placement \| Series B Warrant [Member] \| Exchange [Member]
Subsequent Event [Line Items]
Number of shares issued		5,314,870
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member]
Subsequent Event [Line Items]
Proceeds from private placement	$ 15,000,000
Maximum beneficial ownership percentage		4.99%
Maximum beneficial ownership percentage by election of holder		9.99%
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| New Capital Subscriptions [Member]
Subsequent Event [Line Items]
Number of shares issued		22,727,270
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| Exchange [Member]
Subsequent Event [Line Items]
Number of shares issued		5,314,870
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| Securities Purchase Agreement [Member]
Subsequent Event [Line Items]
Warrant exercise price (in dollars per share)		$ 0.001
Issue and sale of share		28,042,140
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| Private Placement Share [Member]
Subsequent Event [Line Items]
Purchase price of share		$ 0.66
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| Prefunded Warrant [Member]
Subsequent Event [Line Items]
Purchase price of share		0.659
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| Series A Warrant [Member]
Subsequent Event [Line Items]
Warrant exercise price (in dollars per share)		$ 1.32
Expiration period		5 years
Subsequent Event [Member] \| March 2025 Private Placement \| Common Stock [Member] \| Series B Warrant [Member]
Subsequent Event [Line Items]
Warrant exercise price (in dollars per share)		$ 1.98
Expiration period		2 years 6 months