Amount of loss contingency liability.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

Name:	us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Jun. 30, 2019	Apr. 30, 2019
European Patent Office Proceeding [Member]
Other Commitments [Line Items]
Liability related to third party opposition	$ 0
University of Pennsylvania [Member] \| Maximum [Member]
Other Commitments [Line Items]
Upfront fee, milestone fees		$ 20,500,000