Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Assets (Detail)	3 Months Ended
Mar. 31, 2019
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Laboratory Equipment [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Laboratory Equipment [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	7 years
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	remaining life of lease

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 35
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68071081&loc=d3e1205-110223

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790

Name:	us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration