Note 8 - Inventories - Fair Value of Impaired Inventory (Details) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Impairment Data; Total Subdivisions Tested	20	17	17	24	23	33	35	33	40	25	17	14
Impairment Data; Inventory Impairments	$ 10,002	$ 11,098	$ 200	$ 550	$ 620	$ 4,540		$ 4,850	$ 3,873	$ 4,700	$ 1,600		$ 21,850	$ 10,010	$ 10,173
Impairment Data; Fair Value of Inventory After Impairments	$ 32,248	$ 29,874	$ 767	$ 5,223	$ 14,245	$ 52,190		$ 19,952	$ 23,657	$ 12,295	$ 6,415
Impairment Data; Number of Subdivisions Impaired	10	2	1	2	2	9		2	3	2	2
Measurement Input, Discount Rate [Member]
Quantitative Data; Discount Rate			0.12	0.12
Measurement Input, Discount Rate [Member] | Minimum [Member]
Quantitative Data; Discount Rate	0.12	0.12	0.12	0.12	0.1	0.1		0.12	0.12	0.15	0.12		0.12	0.1	0.12
Measurement Input, Discount Rate [Member] | Maximum [Member]
Quantitative Data; Discount Rate	0.18	0.18	0.12	0.12	0.12	0.15		0.18	0.15	0.18	0.15		0.18	0.12	0.15