Description of Business and Basis of Presentation (Details Textual)	1 Months Ended	3 Months Ended				6 Months Ended
	Oct. 11, 2017 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) manufacturing_location contract_manufacturer	Jun. 30, 2017 USD ($)	Jan. 01, 2018 USD ($)	Nov. 16, 2017 USD ($)	Sep. 25, 2017 USD ($)	Dec. 31, 2016 USD ($)
Description of Business and Basis of Presentation (Textual) [Abstract]
Manufacturing locations | manufacturing_location						3
Deferred tax liability recorded associated with unremitted earnings of foreign subsidiary no longer considered indefinitely reinvested		$ 4,900,000				$ 4,900,000
Warranty period, minimum, in years						1 year
Warranty period, maximum, in years						8 years
Accrued warranty liability		1,128,000	$ 1,413,000		$ 2,014,000	$ 1,128,000	$ 2,014,000				$ 1,213,000
Deferred revenue and customer deposits		4,342,000	6,669,000			4,342,000		$ 6,151,000
Cash and cash equivalents		21,547,000	50,122,000			21,547,000
Working capital amount		52,500,000				52,500,000
Cost of revenue		24,036,000			29,350,000	46,771,000	49,928,000
Selling, general and administrative		9,787,000			12,120,000	19,359,000	21,712,000
Research and development		5,549,000			4,449,000	11,081,000	9,155,000
Net Cash Provided by (Used in) Operating Activities						(26,001,000)	(6,502,000)
Value of securities permitted for issuance under shelf registration									$ 125,000,000
Line of Credit [Member]
Description of Business and Basis of Presentation (Textual) [Abstract]
Revolving line of credit		25,000,000.0				25,000,000.0
Borrowings outstanding		5,000,000				5,000,000
Revolving Credit Facility | East West Bank
Description of Business and Basis of Presentation (Textual) [Abstract]
Amount available under revolving line of credit		11,600,000				$ 11,600,000
Minimum
Description of Business and Basis of Presentation (Textual) [Abstract]
Estimated Useful Life (in years)						8 years
Maximum
Description of Business and Basis of Presentation (Textual) [Abstract]
Estimated Useful Life (in years)						14 years
China
Description of Business and Basis of Presentation (Textual) [Abstract]
Number of contract manufacturers | contract_manufacturer						2
Convertible Senior Notes due 2022
Description of Business and Basis of Presentation (Textual) [Abstract]
Proceeds received	$ 43,000,000		5,700,000	$ 37,300,000
Principal amount	$ 6,000,000	$ 46,000,000	$ 46,000,000			$ 46,000,000				$ 40,000,000
Scenario, Adjustment | Accounting Standards Update 2017-07
Description of Business and Basis of Presentation (Textual) [Abstract]
Cost of revenue					74,000		157,000
Selling, general and administrative					50,000		102,000
Research and development					$ 19,000		$ 39,000