Description of Business - Additional Information (Detail) $ in Thousands		9 Months Ended	12 Months Ended
	Jan. 22, 2018	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) Subsidiary	Mar. 31, 2016 USD ($)
Description Of Business [Line Items]
Date of incorporation			Mar. 13, 2014
Number of wholly-owned subsidiaries | Subsidiary			2
Cash		$ 2,669	$ 5,562	$ 2,644
Net loss		12,040	28,024
Accumulated deficit		$ 38,345	$ 66,369
Subsequent Event
Description Of Business [Line Items]
Reverse stock split	1-for-5
Reverse stock split, conversion ratio	5