Note 14 - Provision for Income Taxes (Details) - Effective Income Tax Rate Reconciliation - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Effective Income Tax Rate Reconciliation [Abstract] | |||
| Amount computed using the statutory rate of 35% | $ 18,154 | $ 23,571 | $ 34,072 |
| Section 199 manufacturing deduction | (163) | (2,092) | |
| Agri-biodiesel production credit | (975) | (975) | (1,950) |
| Federal excise tax benefit | (9,958) | (10,344) | (9,566) |
| State excise tax benefit | (792) | (2,409) | (2,067) |
| Credit for increasing research activities | (51) | (80) | (180) |
| Alternative fueling equipment credit | (2) | (23) | |
| Tax exempt interest income | (2) | ||
| State income taxes, net | 695 | 3,189 | 3,983 |
| Tax (benefit)/expense recorded as a decrease/increase in unrecognized tax benefit | (747) | 1,309 | 1,718 |
| Other | (715) | (114) | (576) |
| Provision for income taxes | $ 5,448 | $ 14,145 | $ 23,317 |