Commitments and Contingencies - Additional Information (Detail) $ in Millions		1 Months Ended						3 Months Ended
	Dec. 31, 2017 ft²	Jul. 31, 2018 ft²	Feb. 28, 2017 ft²	Oct. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	May 31, 2016	Sep. 30, 2015 Patent	Jun. 30, 2018 USD ($) ft²	Mar. 31, 2018 ft²
Magnetic Clutch Patents
Commitments and Contingencies [Line Items]
Patents allegedly infringed upon, number | Patent							2
European Pigtail Patent
Commitments and Contingencies [Line Items]
Patents allegedly infringed upon, number | Patent							1
German Pigtail Patent
Commitments and Contingencies [Line Items]
Patents allegedly infringed upon, number | Patent							1
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]
Annual rent expense | $								$ 0.9
Lease expiration date	Aug. 31, 2025		Jul. 31, 2022
Additional office space | ft²	6,607		21,603						11,269
Total office space | ft²								63,343
Lease Agreements | Germany
Commitments and Contingencies [Line Items]
Annual rent expense | $					$ 0.3
Lease commencement period					2017-05
Lease expiration period					2024-05
Lease Agreements | Japan
Commitments and Contingencies [Line Items]
Annual rent expense | $				$ 0.9
Lease expiration period				2021-09
Lease Agreements | Subsequent Event | Massachusetts
Commitments and Contingencies [Line Items]
Lease expiration date		Sep. 30, 2027
Additional office space | ft²		23,864