| 2017 | 2016 | 2015 | ||||||||||
| Income before taxes - U.S. | $ | 16,649 | $ | 40,806 | $ | 51,869 | ||||||
| Provision for income taxes: | ||||||||||||
| Current | 5,766 | (13,014 | ) | 7,475 | ||||||||
| Deferred | (12,213 | ) | (1,437 | ) | (2,283 | ) | ||||||
| State and other | ||||||||||||
| Current | 560 | (1,120 | ) | 487 | ||||||||
| Deferred | (975 | ) | 36 | (231 | ) | |||||||
| Total | $ | (6,862 | ) | $ | (15,535 | ) | $ | 5,448 | ||||
| 2017 | 2016 | 2015 | ||||||||||
| Amount computed using the statutory rate of 35% | $ | 5,788 | $ | 14,282 | $ | 18,154 | ||||||
| Section 199 manufacturing deduction | (85 | ) | - | (163 | ) | |||||||
| Agri-biodiesel production credit | - | (975 | ) | (975 | ) | |||||||
| Federal excise tax benefit | - | (20,048 | ) | (9,958 | ) | |||||||
| State excise tax benefit | - | (6,845 | ) | (792 | ) | |||||||
| Credit for increasing research activities | (127 | ) | (56 | ) | (51 | ) | ||||||
| Dividends received deduction | (865 | ) | (730 | ) | (427 | ) | ||||||
| State income taxes, net | 463 | (1,262 | ) | 695 | ||||||||
| Tax (benefit)/expense recorded as a decrease/increase in unrecognized tax benefit | 191 | 193 | (747 | ) | ||||||||
| Tax Cuts and Jobs A ct of 2017 impact | (12,066 | ) | - | - | ||||||||
| Other | (161 | ) | (94 | ) | (288 | ) | ||||||
| Provision (benefit) for income taxes | $ | (6,862 | ) | $ | (15,535 | ) | $ | 5,448 | ||||
| 2017 | 2016 | |||||||
| Deferred tax assets | ||||||||
| Inventory reserves | $ | 502 | $ | 1,149 | ||||
| Self insurance | 63 | 90 | ||||||
| Asset retirement obligation | 201 | 299 | ||||||
| Deferred revenue | 4,809 | 9,388 | ||||||
| State net operating loss carryforwards | 609 | - | ||||||
| Accrued expenses | 1,674 | - | ||||||
| Stock based compensation | 143 | 77 | ||||||
| Derivative instruments | 252 | 90 | ||||||
| Other | - | 2,546 | ||||||
| Total deferred tax assets | 8,253 | 13,639 | ||||||
| Deferred tax liabilities | ||||||||
| Available for sale securities | (2,285 | ) | (1,376 | ) | ||||
| LIFO inventory | (3,342 | ) | (5,821 | ) | ||||
| Depreciation | (23,293 | ) | (38,293 | ) | ||||
| Other | (382 | ) | (213 | ) | ||||
| Total deferred tax liabilities | (29,302 | ) | (45,703 | ) | ||||
| Valuation allowance | - | - | ||||||
| Net noncurrent deferred tax liabilities | $ | (21,049 | ) | $ | (32,064 | ) | ||
| 2017 | 2016 | |||||||
| As recorded in the consolidated balance sheet | ||||||||
| Noncurrent deferred tax liability | $ | (21,049 | ) | $ | (32,064 | ) | ||
| 2017 | 2016 | 2015 | ||||||||||
| Balance at January 1 | $ | 2,056 | $ | 4,588 | $ | 2,981 | ||||||
| Increases to tax positions taken in the current year | - | 2,056 | 1,471 | |||||||||
| Increases to tax positions taken in a prior year | - | - | 3,117 | |||||||||
| Decrease due to resolution of tax positions taken in a prior year | (2,056 | ) | (4,588 | ) | (2,981 | ) | ||||||
| Balance at December 31 | $ | - | $ | 2,056 | $ | 4,588 | ||||||