Commitments and Contingencies - Additional Information (Detail) $ in Millions		1 Months Ended						12 Months Ended
	Oct. 01, 2018 ft²	Jul. 31, 2018 ft²	Dec. 31, 2017 ft²	Feb. 28, 2017 ft²	Oct. 31, 2016	Sep. 30, 2016	May 31, 2016	Mar. 31, 2019 USD ($)	Mar. 31, 2018 ft²
Patent One
Commitments and Contingencies [Line Items]
Patent expiration period							2020-09
Patent Two
Commitments and Contingencies [Line Items]
Patent expiration period							2020-12
Patent Three
Commitments and Contingencies [Line Items]
Patent expiration period							2021-10
Lease Agreements | Massachusetts
Commitments and Contingencies [Line Items]
Additional office space | ft²		23,864	6,607	21,603					11,269
Lease expiration date		Sep. 30, 2027	Aug. 31, 2025	Jul. 31, 2022
Annual rent expense								$ 0.9
Total office space | ft²	63,343
Lease Agreements | Germany
Commitments and Contingencies [Line Items]
Annual rent expense								0.2
Lease commencement period						2017-05
Lease expiration period						2025-03
Lease Agreements | Japan
Commitments and Contingencies [Line Items]
Annual rent expense								$ 0.9
Lease expiration period					2021-09