Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	3 Months Ended
	Nov. 30, 2017 USD ($) ft²	Dec. 31, 2017 USD ($) € / $	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 USD ($)
Commitments And Contingencies [Line Items]
License agreement commencement date		2006-03	2006-03
Annual minimum payments for licenses		$ 240,000	€ 200,000
Exchange rate relating to license payment | € / $		1.1979
Future minimum payments associated with license		$ 2,400,000
Rent expense related to operating leases		100,000		$ 100,000
Amount deposited into restricted cash account		$ 350,000
Eden Prairie Minnesota [Member]
Commitments And Contingencies [Line Items]
Square feet facility | ft²	36,000
Contractual obligations	$ 4,000,000
Operating lease agreement term	10 years
Operating lease agreement expected commencement date	2018-05
Amount deposited into restricted cash account	$ 400,000
Patents [Member]
Commitments And Contingencies [Line Items]
Patent expiry date		2027-09	2027-09