XML 45 R35.htm IDEA: XBRL DOCUMENT
v3.21.2

Stockholders' Equity - Preferred Stock (Details) - $ / shares | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2021 | Dec. 31, 2020
Class of Stock [Line Items] |  |
Preferred stock, shares authorized (in shares) | 5,000,000 | 5,000,000
Preferred stock, par value (in dollars per share) | $ 0.001 | $ 0.001
Preferred stock, shares outstanding (in shares) | 1,952 | 1,954
Series A Convertible Preferred Stock [Member] |  |
Class of Stock [Line Items] |  |
Preferred stock, shares outstanding (in shares) | 0 | 0
Convertible preferred stock | 3.60% | 3.60%
Series B Convertible Preferred Stock [Member] |  |
Class of Stock [Line Items] |  |
Preferred stock, shares outstanding (in shares) | 1,014 | 1,016
Series B Convertible Preferred Stock [Member] | 2018 Rights Offering [Member] |  |
Class of Stock [Line Items] |  |
Preferred stock, shares outstanding (in shares) | 1,014 |
Number of preferred stock, shares converted | 5,978 |
Series C Convertible Preferred Stock [Member] |  |
Class of Stock [Line Items] |  |
Preferred stock, shares outstanding (in shares) | 938 | 938
Series C Convertible Preferred Stock [Member] | 2018 Rights Offering [Member] |  |
Class of Stock [Line Items] |  |
Preferred stock, shares outstanding (in shares) | 938 |
Number of preferred stock, shares converted | 416,889 |

X
- Definition Number Of Preferred Stock Shares Exercised. + References No definition available. + Details
Name: | pstv_NumberOfPreferredStockSharesExercised
Namespace Prefix: | pstv_
Data Type: | xbrli:sharesItemType
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_ClassOfStockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage rate used to calculate dividend payments on preferred stock. + References No definition available. + Details
Name: | us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer. + References 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(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_PreferredStockParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws. + References 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(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_PreferredStockSharesAuthorized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. + References 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(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_PreferredStockSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=pstv_SeriesAConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=pstv_SeriesBConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ClassOfWarrantOrRightAxis=pstv_TwoThousandEighteenRightsOfferingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=pstv_SeriesCConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |