Note 6 - Income Taxes - Summary of Income Tax Expense at Federal Rate (Details) - USD ($) $ in Thousands |
12 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|||
| Computed tax expense at the statutory rate | $ 41,951 | $ 19,280 | $ 26,349 | ||
| Reduction in income taxes resulting from: | |||||
| Statutory depletion | (3,378) | (1,609) | (1,321) | ||
| State taxes | 397 | 205 | 257 | ||
| Effect of change in statutory tax rate (1) | [1] | 4,519 | |||
| Other, net | 10 | (29) | (41) | ||
| $ 43,499 | $ 17,847 | $ 25,244 | |||
| |||||
| X | ||||||||||
- Definition The amount of statutory deductions for income tax reconciliation. No definition available.
|
| X | ||||||||||
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to state and local income tax expense (benefit). Reference 1: http://www.xbrl.org/2003/role/presentationRef
|