Note 7 - Inventories - Fair Value of Impaired Inventory (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)
Impairment Data; Total Subdivisions Tested	12	16	17	24
Impairment Data; Inventory Impairments	$ 0	$ 610	$ 200	$ 550	$ 610	$ 750
Impairment Data; Fair Value of Inventory After Impairments		$ 10,476	$ 767	$ 5,223
Impairment Data; Number of Subdivisions Impaired	0	2	1	2
Measurement Input, Discount Rate [Member] | Minimum [Member]
Quantitative Data; Discount Rate			0.12	0.12		0.12