Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation —These interim financial statements are unaudited and have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain disclosures have been condensed or omitted from these financial statements. Accordingly, they do not include all the information and notes required by accounting principles generally accepted in the United States of America (“GAAP”) for complete consolidated financial statements, and should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10 -K for the year ended December 31, 2017. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring adjustments, necessary to fairly present the financial position as of, and the results of operations for, all periods presented. In preparing the accompanying financial statements, management has made certain estimates and assumptions that affect reported amounts in the condensed consolidated financial statements and disclosures of contingencies. Actual results may differ from those estimates. The results for interim periods are not necessarily indicative of annual results. Certain reclassifications have been made to the prior period’s consolidated financial statements and related footnotes to conform them to the current period presentation.
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition —Our primary source of revenue is from the sale of coal through contracts with steel producers usually having durations of less than one year. In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014 - 09, Revenue from Contracts with Customers . This new standard supersedes nearly all existing revenue recognition guidance under U.S. GAAP. The core principle of ASU 2014 - 09 is to recognize revenues in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. We adopted ASU 2014 - 09, Revenue from Contracts with Customers, on January 1, 2018 using the modified retrospective method. Before adoption of the new standard, revenue was recognized when risk of loss passed to our customer. The timing of revenue recognition for our coal sales remained consistent between the new and previous standards. There was no material impact on our consolidated financial statements from adopting the new standard but we have expanded disclosure about our revenues. For periods subsequent to January 1, 2018, revenue is recognized when performance obligations under the terms of a contract with our customers are satisfied. This occurs when control of the coal is transferred to our customers. For coal shipments to domestic customers via rail, control is transferred when the railcar is loaded. Control is transferred for export coal shipments to customers via ocean vessel when the vessel is loaded at the port. Our coal sales generally include up to 90 -day payment terms following the transfer of control of the goods to our customer. We do not include extended payment terms in our contracts. Our contracts with customers typically provide for minimum specifications or qualities of the coal we deliver. Variances from these specifications or qualities are settled by means of price adjustments. Generally, these price adjustments are settled within 30 days of delivery and are small. We recognize price adjustments in the period the adjustment is identified.
Earnings Per Share, Policy [Policy Text Block]	Earnings per Share —Basic earnings per share is calculated using our weighted-average outstanding common shares. Diluted earnings per share is calculated using our weighted-average outstanding common shares including the dilutive effect of stock option awards as determined under the treasury stock method. In periods when we have a net loss, stock option awards are excluded from our calculation of earnings per share as their inclusion would have an antidilutive effect.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Financial Instruments —Our financial assets and liabilities consist of cash, accounts receivable, investments, accounts payable and notes payable. The fair values of these instruments approximate their carrying amounts at each reporting date. We invested excess cash amounts before its planned expenditure for capital projects in highly-rated securities with the primary objective of minimizing the potential risk of principal loss. Fair values were determined for each individual security based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the securities. The difference between the carrying amount and fair value of these securities was not material. Nonrecurring fair value measurements include asset retirement obligations, the estimated fair value of which is calculated as the present value of estimated cash flows related to its reclamation liabilities using Level 3 inputs. The significant inputs used to calculate such liabilities include estimates of costs to be incurred, the Company’s credit adjusted discount rate, inflation rates and estimated date of reclamation.
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentrations —During the quarter ended March 31, 2018, sales to three customers accounted for approximately 47% of total revenue. The total balance due from these customers at March 31, 2018 was approximately 62% of total accounts receivable. During the quarter ended March 31, 2017, sales to five customers accounted for all revenue and accounts receivable.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements —In February 2016, the FASB issued ASU 2016 - 02, Leases , which aims to make leasing activities more transparent and comparable and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. This ASU is effective for all interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted. We expect to adopt ASU 2016 - 02 beginning January 1, 2019 and are assessing the impact that this new guidance is expected to have on our financial statements and related disclosures. In September 2016, the FASB issued ASU 2016 - 13, Financial Instruments-Credit Losses . ASU 2016 - 13 was issued to provide more decision-useful information about the expected credit losses on financial instruments and changes the loss impairment methodology. ASU 2016 - 13 is effective for reporting periods beginning after December 15, 2019 using a modified retrospective adoption method. A prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. We are currently assessing the impact this accounting standard will have on our financial statements and related disclosures. In May 2017, the FASB issued ASU 2017 - 09, Modification Accounting for Share-Based Payment Arrangements . The standard amends the scope of modification accounting for share-based payment arrangements and provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under ASC 718. The new standard is effective for fiscal years beginning after December 15, 2017. There was no impact on the financial statements of adopting this new standard on January 1, 2018.