Debt Financing (Details)			3 Months Ended
	Jan. 10, 2018 USD ($)	Jun. 26, 2015	Mar. 31, 2018 USD ($)	Sep. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 24, 2016 CNY (¥)	Jun. 24, 2016 USD ($)
Line of Credit Facility [Line Items]
Restricted cash			$ 1,520,000		$ 1,020,000	$ 6,020,000
Domestic Line of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding			$ 5,243,000		3,004,000
Line of credit, commitment fee percentage			0.25%
Line of credit, remaining borrowing capacity			$ 257,000		1,996,000
China Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity							¥ 6,500,000.0	$ 1,035,000
Line of credit, amount outstanding			0
China Facility | Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)		125.00%
Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding			192,000		246,000
Line of credit, remaining borrowing capacity			843,000		753,000
Amended Amount
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			5,000,000
Letters of credit, amount outstanding			$ 0		$ 0
Amendment 2018 | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	$ 5,500,000
Increase in credit facility	$ 500,000
Forecast | Amendment 2018 | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity				$ 5,000,000