Debt Financing (Details)			3 Months Ended
	Oct. 19, 2018 CNY (¥)	Jun. 29, 2018	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 19, 2018 USD ($)
Domestic Line of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding			$ 5,255,000	$ 5,028,000
Line of credit, commitment fee percentage			0.25%
Line of credit, remaining borrowing capacity			$ 245,000	443,000
China Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity | ¥	¥ 2,625,000.000
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]
Line of credit, remaining borrowing capacity			391,000	382,000
U.S. Domestic Credit Facility | Revolving Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)	3.00%
Amended Amount
Line of Credit Facility [Line Items]
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
China Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity					391,000
Restricted cash					$ 520,000