Description of Business and Basis of Presentation (Details Textual)	3 Months Ended				9 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) manufacturing_location contract_manufacturer segment product_line	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) reporting_unit	Oct. 11, 2017 USD ($)	Sep. 25, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Description of Business and Basis of Presentation (Textual) [Abstract]
Manufacturing locations | manufacturing_location					3
Operating segments | segment					1
Number of product lines | product_line					2
Cumulative valuation allowance			$ 91,000,000		$ 91,000,000
Deferred tax liability recorded associated with unremitted earnings of foreign subsidiary no longer considered indefinitely reinvested			4,900,000		4,900,000
Undistributed earnings of Swiss subsidiary			97,600,000		$ 97,600,000
Number of reporting units | reporting_unit							1
Warranty period, minimum, in years					1 year
Warranty period, maximum, in years					8 years
Accrued warranty liability			2,291,000	$ 1,305,000	$ 2,291,000	$ 1,305,000	$ 1,213,000				$ 1,288,000
Deferred revenue and customer deposits			6,236,000		$ 6,236,000		3,967,000
Term of agreement					10 years
Cash and cash equivalents			52,852,000		$ 52,852,000		$ 25,359,000
Working capital amount			70,200,000		70,200,000
Change in recognition of distributor revenue (less than $1.0 million)			35,816,000	$ 25,506,000	99,605,000	$ 94,844,000
Accounting Standards Update 2016-09, Excess Tax Benefit Component
Description of Business and Basis of Presentation (Textual) [Abstract]
Cumulative valuation allowance			10,000,000		10,000,000
Deferred tax assets related to stock-based compensation			10,000,000		10,000,000
Accounting Standards Update 2016-18
Description of Business and Basis of Presentation (Textual) [Abstract]
Restricted cash balance										$ 100,000	$ 400,000
Revolving Credit Facility | East West Bank
Description of Business and Basis of Presentation (Textual) [Abstract]
Revolving line of credit			25,000,000		25,000,000
Drawings under revolving line of credit			0		0
Amount available under revolving line of credit			12,000,000		$ 12,000,000
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
Revenue from Production Type Contracts | Maximum
Description of Business and Basis of Presentation (Textual) [Abstract]
Percentage of revenue (less than five percent)					5.00%
Revenue | Maximum | Non-product Sale Arrangements
Description of Business and Basis of Presentation (Textual) [Abstract]
Percentage of revenue (less than five percent)					5.00%
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			37,300,000
Principal amount			$ 40,000,000		$ 40,000,000				$ 40,000,000
Interest rate			5.50%		5.50%				5.50%
Convertible Senior Notes due 2022 | Subsequent Event
Description of Business and Basis of Presentation (Textual) [Abstract]
Proceeds received		$ 5,700,000
Principal amount								$ 6,000,000
Scenario, Forecast | Maximum | Accounting Standards Update 2014-09
Description of Business and Basis of Presentation (Textual) [Abstract]
Change in recognition of distributor revenue (less than $1.0 million)	$ 1,000,000