| Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block] |
| Fiscal Year |
|
United States |
|
|
All Foreign Countries |
|
|
Total |
|
| December 31, 2015 |
|
$ |
297,415 |
|
|
$ |
2,196 |
|
|
$ |
299,611 |
|
| December 31, 2014 |
|
$ |
334,210 |
|
|
$ |
7,628 |
|
|
$ |
341,838 |
|
| December 31, 2013 |
|
$ |
430,096 |
|
|
$ |
14,823 |
|
|
$ |
444,919 |
|
|
| Schedule of Segment Reporting Information, by Segment [Table Text Block] |
| |
|
Twelve months ended: |
|
| |
|
2015 |
|
|
2014 |
|
|
2013 |
|
| Revenues: |
|
|
|
|
|
|
|
|
|
|
|
|
| Custom chemicals |
|
$ |
108,160 |
|
|
$ |
127,956 |
|
|
$ |
147,095 |
|
| Performance chemicals |
|
|
17,688 |
|
|
|
18,190 |
|
|
|
14,406 |
|
| Chemicals Revenues |
|
|
125,848 |
|
|
|
146,146 |
|
|
|
161,501 |
|
| Biofuels Revenues |
|
|
173,763 |
|
|
|
195,692 |
|
|
|
283,418 |
|
| Total Revenues |
|
$ |
299,611 |
|
|
$ |
341,838 |
|
|
$ |
444,919 |
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
| Segment gross profit: |
|
|
|
|
|
|
|
|
|
|
|
|
| Chemicals |
|
$ |
35,452 |
|
|
$ |
46,062 |
|
|
$ |
54,708 |
|
| Biofuels |
|
|
21,594 |
|
|
|
19,911 |
|
|
|
45,457 |
|
| Total gross profit |
|
|
57,046 |
|
|
|
65,973 |
|
|
|
100,165 |
|
| Corporate expenses |
|
|
10,075 |
|
|
|
9,845 |
|
|
|
9,911 |
|
| Income before interest and taxes |
|
|
46,971 |
|
|
|
56,128 |
|
|
|
90,254 |
|
| Interest and other income |
|
|
5,213 |
|
|
|
6,877 |
|
|
|
5,875 |
|
| Interest and other expense |
|
|
(315 |
) |
|
|
4,340 |
|
|
|
1,222 |
|
| Provision for income taxes |
|
|
(5,448 |
) |
|
|
(14,145 |
) |
|
|
(23,317 |
) |
| Net income |
|
$ |
46,421 |
|
|
$ |
53,200 |
|
|
$ |
74,034 |
|
|