XML 87 R54.htm IDEA: XBRL DOCUMENT
v3.19.2

Asset Purchase Agreement with Azaya Therapeutics - Additional Information (Details) - Assets Purchased from Azaya Therapeutics, Inc. [Member] | Feb. 15, 2017 USD ($) Candidate Employee shares | Dec. 31, 2017 USD ($)
--- | --- | ---
Business Acquisition [Line Items] |  |
Obligation to pay on existing payables assumed | $ 1,796,000 |
Total consideration | 4,272,000 |
Fair value of the common stock issued | 2,311,000 |
Assumed liabilities | 1,800,000 |
Acquisition costs | 200,000 |
Asset Purchase Agreement |  |
Business Acquisition [Line Items] |  |
Book value of tangible assets acquired | $ 3,000,000 |
Common stock, shares issued | shares | 117,325 |
Common stock, shares issued after closing date | shares | 87,994 |
Common stock deposited in escrow | shares | 29,331 |
Obligation to pay on existing payables assumed | $ 1,800,000 |
Existing payables, paid during the period |  | $ 1,800,000
Number of employees | Employee | 0 |
Maximum earn-out payment obligations | $ 100,000,000 |
Aggregate payment obligation threshold limit | $ 50,000,000 |
Percentage of net sales deemed for purposes of calculating payments | 50.00% |
Asset Purchase Agreement | IPR&D [Member] |  |
Business Acquisition [Line Items] |  |
Number of drug candidates acquired | Candidate | 2 |

X
- Definition Aggregate payment obligation threshold limit for payment to counter party. + References No definition available. + Details
Name: | pstv_AggregatePaymentObligationThresholdLimitForPaymentToCounterParty
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Business combination contingent consideration assets acquired liabilities assumed payment made during the period. + References No definition available. + Details
Name: | pstv_BusinessCombinationContingentConsiderationAssetsAcquiredLiabilitiesAssumedPaymentMadeDuringPeriod
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business combination recognized identifiable assets acquired and liabilities assumed consideration. + References No definition available. + Details
Name: | pstv_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedConsideration
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business combination recognized identifiable assets acquired and liabilities assumed fair value of common stock issued. + References No definition available. + Details
Name: | pstv_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFairValueOfCommonStockIssued
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum earn-out payment obligations. + References No definition available. + Details
Name: | pstv_MaximumEarnOutPaymentObligations
Namespace Prefix: | pstv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number of drug candidates acquired. + References No definition available. + Details
Name: | pstv_NumberOfDrugCandidatesAcquired
Namespace Prefix: | pstv_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of employees. + References No definition available. + Details
Name: | pstv_NumberOfEmployees
Namespace Prefix: | pstv_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of net sales deemed for purpose of calculating commercialization milestone and earn-out payment. + References No definition available. + Details
Name: | pstv_PercentageOfNetSalesDeemedForPurposeOfCalculatingCommercializationMilestoneAndEarnOutPayment
Namespace Prefix: | pstv_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition. + References No definition available. + Details
Name: | us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of shares of equity interests issued or issuable to acquire entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(4) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix: | us-gaap_
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_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of liabilities incurred for goods and services received that are used in an entity's business and related party payables, assumed at the acquisition date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of liabilities assumed at the acquisition date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value of assets acquired in noncash investing or financing activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586 + Details
Name: | us-gaap_FairValueOfAssetsAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The number of shares issued as [noncash or part noncash] consideration for a business or asset acquired. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586 + Details
Name: | us-gaap_NoncashOrPartNoncashAcquisitionNoncashFinancialOrEquityInstrumentConsiderationSharesIssued1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Shares issuable for little or no cash consideration upon the satisfaction of certain conditions (contingently issuable shares) are considered outstanding common shares and included in the computation of basic Earnings Per Share as of the date that all necessary conditions have been satisfied (in essence, when issuance of the shares is no longer contingent). Outstanding common shares that are contingently returnable (that is, subject to recall) are treated in the same manner as contingently issuable shares. Contingently issuable shares include shares that (a) will be issued in the future upon the satisfaction of specified conditions, (b) have been placed in escrow and all or part must be returned if specified conditions are not met, or (c) have been issued but the holder must return all or part if specified conditions are not met. The number of contingently issuable shares is determined by relating the portion of time within a reporting period that these shares have been outstanding to the total time in that period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e2646-109256 + Details
Name: | us-gaap_WeightedAverageNumberOfSharesContingentlyIssuable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=pstv_AssetsPurchasedFromAzayaTherapeuticsIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TypeOfArrangementAxis=pstv_AssetPurchaseAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_InProcessResearchAndDevelopmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |