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	Mar. 31, 2020	Dec. 31, 2019
Cash and cash equivalents	$ 55,908	$ 59,977
Restricted cash	6,609	7,051
Total assets	62,517	67,028
Bank acceptance payable	9,550	6,310
Convertible senior notes	59,973	77,191
Total liabilities	69,523	83,501
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	55,908	59,977
Restricted cash	6,609	7,051
Total assets	62,517	67,028
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
Total assets	0	0
Bank acceptance payable	9,550	6,310
Convertible senior notes	59,973	77,191
Total liabilities	69,523	83,501
Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Total assets	0	0
Bank acceptance payable	0	0
Convertible senior notes	0	0
Total liabilities	$ 0	$ 0