Description of Business and Basis of Presentation (Details Textual) $ / shares in Units, shares in Thousands	1 Months Ended		3 Months Ended			9 Months Ended
	Aug. 31, 2018 USD ($) $ / shares shares	Oct. 11, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) manufacturing_location contract_manufacturer	Sep. 30, 2017 USD ($)	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			1,101,000	$ 1,413,000	$ 2,291,000	$ 1,101,000	$ 2,291,000			$ 1,213,000
Cash and cash equivalents			23,561,000	50,122,000		23,561,000
Working capital amount			67,100,000			67,100,000
Cost of revenue			27,357,000		28,492,000	74,128,000	78,420,000
Selling, general and administrative			9,052,000		14,565,000	28,411,000	36,277,000
Research and development			5,599,000		4,909,000	16,680,000	14,064,000
Offering shares of common stock | shares	7,590
Offering price per share | $ / shares	$ 3.25
Proceeds from sale of common stock, net of offering costs	$ 23,000,000					22,974,000	0
Use of cash from operations						(40,046,000)	(8,776,000)
Value of securities permitted for issuance under shelf registration								$ 125,000,000
Value of securities issued under shelf registration			24,700,000			24,700,000
Value of securities remaining available for issuance under shelf registration			100,300,000			100,300,000
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			0			0
Revolving Credit Facility | East West Bank
Description of Business and Basis of Presentation (Textual) [Abstract]
Amount available under revolving line of credit			16,300,000			$ 16,300,000
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					72,000		229,000
Selling, general and administrative					51,000		153,000
Research and development					$ 18,000		$ 57,000