Note 22 - Segment Information - Summary of Business by Segment (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2019	[1]	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	[1]	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 20,177		$ 65,684	$ 70,864	$ 48,501	$ 65,513	$ 81,422	$ 88,336	$ 55,747		$ 205,226	$ 291,018	$ 275,026
Gross profit	$ 62,145		$ 5,462	$ 3,270	$ 3,262	$ 14,967	$ 12,653	$ 8,271	$ 37,507		74,139	73,398	20,261
Operating Segments [Member] | Chemicals [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total											104,827	117,128	105,386
Gross profit											29,923	33,986	28,016
Operating Segments [Member] | Chemicals [Member] | Custom Chemicals [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total											90,962	97,746	87,905
Operating Segments [Member] | Chemicals [Member] | Performance Chemicals [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total											13,865	19,382	17,481
Operating Segments [Member] | Biofuels [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total											100,399	173,890	169,640
Gross profit											$ 44,216	$ 39,412	$ (7,755)

[1] The fourth quarter of 2019 and the first quarter of 2018 includes the retroactive reinstatement of the BTC in revenue and gross profit (see Note 3 for further information).