XML 33 R24.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Fair Value Measurements - Additional Information (Details) | 9 Months Ended
--- | ---
Sep. 30, 2022
Series U Warrants [Member] |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |
Warrants issued, underwritten public offering, period | 2019-09

X
- Definition Warrants issued, underwritten public offering, period. + References No definition available. + Details
Name: | pstv_WarrantsIssuedUnderwrittenPublicOfferingPeriod
Namespace Prefix: | pstv_
Data Type: | xbrli:gYearMonthItemType
Balance Type: | na
Period Type: | duration

X
- 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=pstv_SeriesUWarrantsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |