Commitments and Contingencies (Details) $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2017	Mar. 31, 2018 USD ($) ft²	Mar. 31, 2017 USD ($)
Product Warranty [Abstract]
Period of warranty		12 months
Change in warranty accrual [Roll Forward]
Beginning accrued product warranty		$ 133	$ 251
Accruals for warranties issued		59	33
Adjustments related to pre-existing warranties including expirations and changes in estimates		(46)	(105)
Cost of warranty repair		(29)	(46)
Ending accrued product warranty		$ 117	$ 133
Leases [Abstract]
Area of property under long-term operating lease (in square feet) | ft²		19,467
Additional years per lease option		3 years
Number of additional years to lease term	3 years
Term of royalty agreement		8 years
Aggregate amount payable towards royalty		$ 7,000
Operating leases
Less than 1 year		226
1-3 years		299
4-5 years		25
Total		550
Royalty agreement
Less than 1 year		431
Total		431
Total
Less than 1 year		657
1-3 years		299
4-5 years		25
Total		981
Dingxing
Leases [Abstract]
Total investment agreement value		90,000
Kazuo
Leases [Abstract]
Total investment agreement value		$ 15,000