Note 10 - Fair Value of Financial Instruments - Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cash and cash equivalents	$ 44,013	$ 43,425
Restricted cash	6,486	6,689
Note receivable	3,819	401
Total assets	54,318	50,515
Bank acceptance payable	6,469	15,860
Convertible senior notes	70,265	70,225
Total liabilities	76,734	86,085
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	44,013	43,425
Restricted cash	6,486	6,689
Note receivable	0	0
Total assets	50,499	50,114
Bank acceptance payable	0	0
Convertible senior notes	0	0
Total liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Note receivable	3,819	401
Total assets	3,819	401
Bank acceptance payable	6,469	15,860
Convertible senior notes	70,265	70,225
Total liabilities	76,734	86,085
Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Note receivable	0	0
Total assets	0	0
Bank acceptance payable	0	0
Convertible senior notes	0	0
Total liabilities	$ 0	$ 0