Convertible Senior Notes (Details)			3 Months Ended	9 Months Ended
	Mar. 05, 2019 USD ($) item	Feb. 28, 2019 $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018
Debt Instrument [Line Items]
Proceeds from sale of notes after deducting the Initial Purchaser's discounts and offering expenses				$ 76,362,000
Net carrying amount			$ 76,835,000	76,835,000
Interest expense
Amortization of debt issuance costs				673,000
Convertible senior notes due 2024
Debt Instrument [Line Items]
Interest rate	5.00%
Proceeds from sale of notes after deducting the Initial Purchaser's discounts and offering expenses	$ 76,400,000
Repayments of capital expenditure loan and real estate term loan	37,800,000
Principal	$ 80,500,000		80,500,000	80,500,000
Unamortized debt issuance costs			(3,665,000)	(3,665,000)
Net carrying amount			76,835,000	76,835,000
Initial conversion rate	56.9801%
Initial conversion price | $ / shares		$ 17.55
Initial conversion premium		30.00%
Share price | $ / shares		$ 13.50
Percentage of sale price per share to conversion price	130.00%
Number of trading days | item	20
Number of consecutive trading days	30
Redemption price as percentage of principal amount	100.00%
Transaction costs			4,100,000	4,100,000
Interest expense
Contractual interest expense			984,000	2,270,000
Amortization of debt issuance costs			207,000	473,000
Total interest cost			$ 1,191,000	$ 2,743,000
Effective interest rate			5.10%	5.10%	0.00%