Commitments and Contingencies - Additional Information (Detail) $ in Millions				1 Months Ended				3 Months Ended	9 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)	Aug. 12, 2016 ft²	Dec. 31, 2015 USD ($)	Oct. 31, 2015 ft²	Sep. 30, 2015 Patent	Jul. 31, 2013 ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)	Apr. 30, 2014 USD ($)
Commitments and Contingencies [Line Items]
Purchase price of property amount				$ 16.5
License agreement, upfront payment											$ 1.5
License agreement, maximum agreed additional payments upon achievement of development milestones											$ 4.5
Thoratec
Commitments and Contingencies [Line Items]
Contingent liability	$ 2.3							$ 2.3	$ 2.3
Magnetic Clutch Patents
Commitments and Contingencies [Line Items]
Patents allegedly infringed upon, number | Patent						2
Pigtail Patents
Commitments and Contingencies [Line Items]
Patents allegedly infringed upon, number | Patent						2
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
Research and Development Expenses
Commitments and Contingencies [Line Items]
License agreement, development milestones payment								0.8	$ 0.8
Europe
Commitments and Contingencies [Line Items]
Purchase price of property amount	11.6	€ 11,000,000
Facilities leases, base rent per month	$ 0.1							$ 0.1	$ 0.1	€ 65,000
Lease Agreements
Commitments and Contingencies [Line Items]
Office space under capital lease | ft²			163,560
Lease agreement termination date			Aug. 31, 2026
Lease description									The Company has options to extend the initial term for three separate periods of five years each.
Capital lease term									15 years
Lease Agreements | Europe
Commitments and Contingencies [Line Items]
Office space under operating lease | ft²							33,000
Lease, expiration date							Jul. 31, 2023
Additional office space under operating lease | ft²					9,000
Lease Agreements | Japan
Commitments and Contingencies [Line Items]
Annual rent expense									$ 0.9
Lease Agreement Adjacent To Aachen Facility | Europe
Commitments and Contingencies [Line Items]
Office space under operating lease | ft²					30,000
Lease, expiration date					Jun. 30, 2017