Related Parties - Additional Information (Detail)	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) Agreement	Dec. 31, 2017 USD ($) Agreement	Mar. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Number of related parties agreement entered | Agreement		2	2
Cirius Tx, Inc., [Member]
Related Party Transaction [Line Items]
Amount of transactions with related party for providing services		$ 44,000	$ 94,000
Cirius Tx, Inc., [Member] | Scenario, Forecast [Member]
Related Party Transaction [Line Items]
Amount of transactions with related party for providing services	$ 74,000
Viscient Biosciences [Member]
Related Party Transaction [Line Items]
Revenue recognized from related parties agreement		$ 323,000	$ 323,000
Viscient Biosciences [Member] | Scenario, Forecast [Member]
Related Party Transaction [Line Items]
Amount of transactions with related party for providing services				$ 323,000