SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
Mar. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	consolidated financial statements include our accounts and those of our wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. In the opinion of management, all adjustments, consisting of normal recurring accruals considered necessary for a fair presentation of interim financial information, have been included.
Use of Estimates	The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions. Significant estimates include, but are not limited to, those for proven and probable mineral reserves, the related present value of estimated future net cash flows, useful lives of plant assets, asset retirement obligations, normal inventory production levels, inventory valuations, the valuation of equity awards, the valuation of receivables, valuation of our deferred tax assets and estimated blended income tax rates utilized in the current and deferred income tax calculations. There are numerous uncertainties inherent in estimating quantities of proven and probable reserves, projecting future rates of production, and the timing of development expenditures. Future mineral prices may vary significantly from the prices in effect at the time the estimates are made, as may estimates of future operating costs. The estimate of proven and probable mineral reserves, the related present value of estimated future cash flows, and useful lives of plant assets can affect various other items including depletion, the net carrying value of our mineral properties, the useful lives of related property, plant, and equipment, depreciation expense, and estimates associated with recoverability of long-lived assets and asset retirement obligations. Specific to income tax items, we experience fluctuations in the valuation of the deferred tax assets and liabilities due to changing state income tax rates and the blend of state tax rates.
Revenue Recognition	Revenue is recognized when evidence of an arrangement exists, risks and rewards of ownership have been transferred to customers, which is generally when title passes, the selling price is fixed and determinable, and collection is reasonably assured. Title passes at the designated shipping point for the majority of sales, but, in a few cases, title passes at the delivery destination. The shipping point may be the plant, a distribution warehouse, a customer warehouse, or a port. Title passes for some international shipments upon payment by the purchaser; however, revenue is not recognized for these transactions until shipment because the risks and rewards of ownership have not transferred pursuant to a contractual arrangement. Prices are generally set at the time of, or prior to, shipment. In cases where the final price is determined upon resale of the product by the customer, revenue is deferred until the final sales price is known. Sales are reported on a gross basis. We quote prices to customers both on a delivered basis and on the basis of pick-up at our plants and warehouses. When a sale occurs on a delivered basis, we incur and, in turn, bill the customer and record as gross revenue the product sales value, freight, packaging, and certain other distribution costs. Many customers, however, arrange and pay for these costs directly and, in these situations, only the product sales are included in gross revenues.
By-Product Credits	When by-product inventories are sold, we record the sale of by-products as a credit to cost of goods sold.
Fair Value of Financial Instruments	financial instruments include cash and cash equivalents, short-term and long-term investments, restricted cash, accounts receivable, refundable income taxes, and accounts payable. These instruments are carried at cost, which approximates fair value due to the short-term maturities of the instruments. All available-for-sale investments are carried at fair value. Allowances for doubtful accounts are recorded against the accounts receivable balance to estimate net realizable value. The fair value of the long-term debt is estimated using discounted cash flow analysis based on current borrowing rates for debt with similar remaining maturities and ratings. Although there are no amounts currently outstanding under our unsecured credit facility, any borrowings that become outstanding would bear interest at a floating rate and therefore be recorded at their estimated fair value.
(Loss) Earnings per Share	Basic net income or loss per common share of stock is calculated by dividing net income or loss available to common stockholders by the weighted average basic common shares outstanding for the respective period. Diluted net income or loss per common share of stock is calculated by dividing net income or loss by the weighted average diluted common shares outstanding, which includes the effect of potentially dilutive securities. Potentially dilutive securities for the diluted earnings or loss per share calculation consist of awards of non-vested restricted shares of common stock, non-vested performance units, and non-qualified stock options. The dilutive effect of stock based compensation arrangements are computed using the treasury stock method. Following the lapse of the vesting period of restricted shares of common stock, the shares are considered issued and therefore are included in the number of issued and outstanding shares for purposes of these calculations.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

3 Months Ended

Mar. 31, 2015

consolidated financial statements include our accounts and those of our wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. In the opinion of management, all adjustments, consisting of normal recurring accruals considered necessary for a fair presentation of interim financial information, have been included.

Use of Estimates

The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions.

Significant estimates include, but are not limited to, those for proven and probable mineral reserves, the related present value of estimated future net cash flows, useful lives of plant assets, asset retirement obligations, normal inventory production levels, inventory valuations, the valuation of equity awards, the valuation of receivables, valuation of our deferred tax assets and estimated blended income tax rates utilized in the current and deferred income tax calculations. There are numerous uncertainties inherent in estimating quantities of proven and probable reserves, projecting future rates of production, and the timing of development expenditures. Future mineral prices may vary significantly from the prices in effect at the time the estimates are made, as may estimates of future operating costs. The estimate of proven and probable mineral reserves, the related present value of estimated future cash flows, and useful lives of plant assets can affect various other items including depletion, the net carrying value of our mineral properties, the useful lives of related property, plant, and equipment, depreciation expense, and estimates associated with recoverability of long-lived assets and asset retirement obligations. Specific to income tax items, we experience fluctuations in the valuation of the deferred tax assets and liabilities due to changing state income tax rates and the blend of state tax rates.

Revenue Recognition

Revenue is recognized when evidence of an arrangement exists, risks and rewards of ownership have been transferred to customers, which is generally when title passes, the selling price is fixed and determinable, and collection is reasonably assured. Title passes at the designated shipping point for the majority of sales, but, in a few cases, title passes at the delivery destination. The shipping point may be the plant, a distribution warehouse, a customer warehouse, or a port. Title passes for some international shipments upon payment by the purchaser; however, revenue is not recognized for these transactions until shipment because the risks and rewards of ownership have not transferred pursuant to a contractual arrangement. Prices are generally set at the time of, or prior to, shipment. In cases where the final price is determined upon resale of the product by the customer, revenue is deferred until the final sales price is known.

Sales are reported on a gross basis. We quote prices to customers both on a delivered basis and on the basis of pick-up at our plants and warehouses. When a sale occurs on a delivered basis, we incur and, in turn, bill the customer and record as gross revenue the product sales value, freight, packaging, and certain other distribution costs. Many customers, however, arrange and pay for these costs directly and, in these situations, only the product sales are included in gross revenues.

By-Product Credits

When by-product inventories are sold, we record the sale of by-products as a credit to cost of goods sold.

Fair Value of Financial Instruments

financial instruments include cash and cash equivalents, short-term and long-term investments, restricted cash, accounts receivable, refundable income taxes, and accounts payable. These instruments are carried at cost, which approximates fair value due to the short-term maturities of the instruments. All available-for-sale investments are carried at fair value. Allowances for doubtful accounts are recorded against the accounts receivable balance to estimate net realizable value. The fair value of the long-term debt is estimated using discounted cash flow analysis based on current borrowing rates for debt with similar remaining maturities and ratings. Although there are no amounts currently outstanding under our unsecured credit facility, any borrowings that become outstanding would bear interest at a floating rate and therefore be recorded at their estimated fair value.

(Loss) Earnings per Share

Basic net income or loss per common share of stock is calculated by dividing net income or loss available to common stockholders by the weighted average basic common shares outstanding for the respective period.

Diluted net income or loss per common share of stock is calculated by dividing net income or loss by the weighted average diluted common shares outstanding, which includes the effect of potentially dilutive securities. Potentially dilutive securities for the diluted earnings or loss per share calculation consist of awards of non-vested restricted shares of common stock, non-vested performance units, and non-qualified stock options. The dilutive effect of stock based compensation arrangements are computed using the treasury stock method. Following the lapse of the vesting period of restricted shares of common stock, the shares are considered issued and therefore are included in the number of issued and outstanding shares for purposes of these calculations.

- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

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- Definition

Disclosure of accounting policy for computing basic and diluted earnings or loss per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements.

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- Definition

Disclosure of accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction is generally disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.

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