Debt Financing (Details)			9 Months Ended
	Oct. 19, 2018 USD ($)	Jun. 29, 2018 CNY (¥)	Sep. 30, 2018 USD ($)	Oct. 19, 2018 CNY (¥)	Oct. 19, 2018 USD ($)	Sep. 01, 2018 USD ($)	Jun. 29, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 16, 2017 USD ($)
Line of Credit Facility [Line Items]
Restricted cash			$ 6,520,000					$ 1,020,000	$ 1,020,000
Domestic Line of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding			$ 5,053,000					3,004,000
Line of credit, commitment fee percentage			0.25%
Line of credit, remaining borrowing capacity			$ 447,000					1,996,000
China Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		¥ 5,250,000.000					$ 765,000
Restricted cash			1,020,000
Line of credit, amount outstanding			0
China Facility | Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)		140.00%
Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding			0					246,000
Line of credit, remaining borrowing capacity			765,000					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						$ 5,000,000
Subsequent Event | China Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity				¥ 2,625,000.000	$ 383,000
Restricted cash					520,000
Subsequent Event | 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