Long-Term Debt (Details Textual)		12 Months Ended
	Feb. 16, 2018 USD ($)	Dec. 31, 2019 USD ($) day $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Capitalization, Long-term Debt [Line Items]
Proceeds from loans or conditional grants		$ 0	$ 143,750,000	$ 0
ADS, option price per share (in dollars per share) | $ / shares		$ 10.79
ADS premium percentage		20.00%
ADS purchased, price per share (in dollars per share) | $ / shares		$ 8.99
Convertible Debt
Schedule of Capitalization, Long-term Debt [Line Items]
Remaining discount amortization period		5 years
4.50% Exchangeable Senior Notes Due 2023
Schedule of Capitalization, Long-term Debt [Line Items]
Debt instrument, face amount	$ 125,000,000
Interest rate	4.50%	4.50%	4.50%
Option to increase aggregate principal amount	$ 18,750,000
Proceeds from loans or conditional grants	$ 137,560,000
ADSs, conversion ratio		92.6956
4.50% Exchangeable Senior Notes Due 2023 | Convertible Debt
Schedule of Capitalization, Long-term Debt [Line Items]
Debt discount and issuance costs, net		$ 6,190,000
Debt issuance cost allocated to equity component		1,201,000
Debt issuance cost allocated to liability component		$ 4,989,000
Debt Instrument, Redemption, Period One
Schedule of Capitalization, Long-term Debt [Line Items]
Consecutive business days		5 days
Consecutive trading days | day		5
Debt Instrument, Redemption, Period Two
Schedule of Capitalization, Long-term Debt [Line Items]
Scheduled threshold trading days		95 days
Threshold trading days | day		35
Debt Instrument, Redemption, Period Three
Schedule of Capitalization, Long-term Debt [Line Items]
Consecutive trading days | day		30
Threshold trading days | day		20
Threshold percentage of stock price trigger		130.00%