XML 64 R52.htm IDEA: XBRL DOCUMENT
v3.20.4

Term Loan Obligations (Details) - USD ($) |  |  |  | 12 Months Ended
--- | --- | --- | --- | ---
Mar. 29, 2020 | Mar. 28, 2020 | May 29, 2015 | Dec. 31, 2020 | Dec. 31, 2019
Debt Instrument [Line Items] |  |  |  |  |
Warrant exercise price (in dollars per share) |  |  |  | $ 2.25 |
Interest expense |  |  |  | $ 1,107,000 | $ 1,855,000
Non-cash amortization |  |  |  | $ 600,000 | $ 500,000
LIBOR [Member] | Interest Rate Floor [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Basis variable rate |  |  | 1.00% |  |
Term Loan [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Origination Date |  |  |  | May 29, 2015 | May 29, 2015
Original Loan Amount |  |  | $ 17,700,000 | $ 17,700,000 | $ 17,700,000
Basis variable rate |  |  | 7.95% |  |
Maturity date | Sep. 01, 2024 | Sep. 01, 2021 | May 01, 2021 |  |
Fees amount associated with loan |  |  | $ 3,200,000 | $ 3,200,000 |
Number of securities called by warrant or right |  |  | 188 |  |
Warrant exercise price (in dollars per share) |  |  | $ 5,175 |  |
Date from which warrants are exercisable |  |  |  |  | Nov. 30, 2015
Warrant expiration date |  |  |  |  | May 29, 2025
Minimum liquidity covenant |  |  |  |  | $ 2,000,000
Debt principal repayment start date | May 01, 2021 | May 01, 2020 |  |  |
Prepayments of term loan | $ 5,000,000 |  |  |  |
Related final payment | 300,000 |  |  |  |
Term loan, remaining amount | 4,300,000 |  |  |  |
Amendment fee | $ 1,000,000 |  |  |  |
Debt Instrument, Covenant Compliance |  |  |  | the Company was in compliance with all of the debt covenants under the Loan and Security Agreement. |
Term Loan [Member] | Loan and Security Agreement [Member] | Sale of the Japanese Subsidiary and Certain Assets [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Payments for principal, interest and fees |  |  | $ 3,100,000 |  |
Minimum [Member] | Term Loan [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate |  |  | 8.95% |  |
Maximum [Member] | Term Loan [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Original Loan Amount |  |  |  | $ 3,000,000 |
Long Term Debt Outstanding Threshold Amount |  |  |  | $ 4,300,000 |

X
- Definition The date that the warrant or right expires. + References No definition available. + Details
Name: | pstv_ClassOfWarrantOrRightExpirationDate
Namespace Prefix: | pstv_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Debt instrument amendment fee. + References No definition available. + Details
Name: | pstv_DebtInstrumentAmendmentFee
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Floating interest rate for funds borrowed, under the debt agreement. + References No definition available. + Details
Name: | pstv_DebtInstrumentFloatingInterestRatePercentage
Namespace Prefix: | pstv_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Debt principal repayment start date. + References No definition available. + Details
Name: | pstv_DebtPrincipalRepaymentStartDate
Namespace Prefix: | pstv_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Long term debt outstanding threshold amount. + References No definition available. + Details
Name: | pstv_LongTermDebtOutstandingThresholdAmount
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Long term debt remaining amount. + References No definition available. + Details
Name: | pstv_LongTermDebtRemainingAmount
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Minimum liquidity covenant amount. + References No definition available. + Details
Name: | pstv_MinimumLiquidityCovenantAmount
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Prepayments of long term debt. + References No definition available. + Details
Name: | pstv_PrepaymentsOfLongTermDebt
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Related final payment + References No definition available. + Details
Name: | pstv_RelatedFinalPayment
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details
Name: | us-gaap_AmortizationOfDebtDiscountPremium
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Date the warrants or rights are exercisable, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
Name: | us-gaap_ClassOfWarrantOrRighstDateFromWhichWarrantsOrRightsExercisable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Exercise price per share or per unit of warrants or rights outstanding. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
Name: | us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- 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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
Name: | us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition States whether the entity was in compliance with the debt covenants throughout the reporting period, and describes facts and circumstances of any compliance failure. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823 Reference 2: 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(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentCovenantCompliance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of the fee that accompanies borrowing money under the debt instrument. + 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 210.5-02.22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentFeeAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_DebtInstrumentMaturityDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Date the debt instrument was offered for sale, in CCYY-MM-DD format. + 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(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 + Details
Name: | us-gaap_DebtInstrumentOfferingDate1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of the cost of borrowed funds accounted for as interest expense. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (210.5-03(11)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.9) -URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 + Details
Name: | us-gaap_InterestExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Cash payments for and related to principal collection on loans related to operating activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585 + Details
Name: | us-gaap_PaymentsForLoans
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateFloorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=pstv_TermLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=pstv_LoanAndSecurityAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DisposalGroupClassificationAxis=pstv_SaleOfJapaneseSubsidiaryAndCertainAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |