Nature of the Business and Basis of Presentation - Additional Information (Detail)		1 Months Ended
Mar. 13, 2019	Aug. 31, 2015
Schedule Of Accounting Policies [Line Items]
Percentage of common stock owned	64.00%
Reverse stock split, conversion ratio	0.1667	0.1667
Arsanis
Schedule Of Accounting Policies [Line Items]
Business acquisition share exchange ratio	0.5702

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Name:	us-gaap_StockholdersEquityNoteStockSplitConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration