Quarterly Financial Data - Summary of Quarterly Results of Operations (Parenthetical) (Detail) $ in Millions	Dec. 31, 2016 USD ($)
Pfizer [Member]
Quarterly Financial Data [Line Items]
Revenue recognized upon termination of Pfizer collaboration and license agreement	$ 5.6

Revenue recognized upon termination of collaboration agreement.

No definition available.

Name:	psdv_RevenueRecognizedUponTerminationOfCollaborationAgreement
Namespace Prefix:	psdv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant