Description of Business and Summary of Significant Accounting Policies (Textual) (Details)			3 Months Ended	12 Months Ended
	Oct. 11, 2017 USD ($)	Sep. 25, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) manufacturing_location contract_manufacturer product_line	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 CHF (SFr)	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2014 USD ($)
Description of Business and Summary of Significant Accounting Policies [Line Items]
Proceeds from long-term debt, net of discount and issuance costs				$ 42,991,000	$ 0	$ 3,040,000
Manufacturing locations | manufacturing_location				3
Cash and cash equivalents			$ 25,359,000		25,359,000			$ 50,122,000
Working capital								68,400,000
Total deferred revenue and customer deposits			3,967,000		3,967,000			6,669,000
Leasehold improvements funded by landlords			1,700,000		1,700,000			1,400,000
Deferred rent related to leasehold improvements funding by landlords			1,700,000		1,700,000			1,400,000
Goodwill impairment				$ 0	0	0
Impairment of assets			1,200,000	$ 240,000	1,389,000	0
Standard product warranty, term, minimum				1 year
Standard product warranty, term, maximum				8 years
Accrued warranty			1,213,000		1,213,000	1,288,000		1,413,000
FDIC insurance limit								250,000
Switzerland non-government financial institutions insured amount | SFr							SFr 100,000
Research and development expense				$ 18,351,000	20,889,000	24,697,000
Third party funding offset				2,800,000	1,200,000	1,300,000
Advertising expense				700,000	700,000	1,100,000
Cash, cash equivalents and restricted cash, beginning of period			25,359,000		25,359,000	24,782,000		50,122,000		$ 24,732,000
Valuation allowance			78,366,000		78,366,000			61,403,000
Loss from operations				37,896,000	25,886,000	$ 17,005,000
Accounting Standards Update 2016-09, Excess Tax Benefit Component
Description of Business and Summary of Significant Accounting Policies [Line Items]
Recognition of deferred tax assets									$ 10,000,000
Valuation allowance									$ 10,000,000
Accounting Standards Update 2016-18
Description of Business and Summary of Significant Accounting Policies [Line Items]
Cash, cash equivalents and restricted cash, beginning of period			$ 400,000		400,000
Accounting Standards Update 2017-07
Description of Business and Summary of Significant Accounting Policies [Line Items]
Loss from operations				700,000	500,000
Joint Development Agreement for Technologies for Automotive Market
Description of Business and Summary of Significant Accounting Policies [Line Items]
Cash consideration under joint development agreement				$ 2,200,000	$ 600,000
Minimum
Description of Business and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				3 years
Estimated Useful Life (in years)				8 years
Maximum
Description of Business and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				10 years
Estimated Useful Life (in years)				14 years
High Reliability
Description of Business and Summary of Significant Accounting Policies [Line Items]
Number of product lines | product_line				2
China
Description of Business and Summary of Significant Accounting Policies [Line Items]
Number of contract manufacturers | contract_manufacturer				2
Convertible Senior Notes due 2022
Description of Business and Summary of Significant Accounting Policies [Line Items]
Convertible Senior Notes due 2022, aggregate principal	$ 6,000,000.0	$ 40,000,000						$ 46,000,000
Interest rate		5.50%					5.50%	5.50%
Proceeds from long-term debt, net of discount and issuance costs	$ 5,700,000	$ 37,300,000