Bank Debt (Narrative) (Details)	12 Months Ended
Dec. 31, 2015 USD ($) agreement
Debt Instrument [Line Items]
Credit agreement, amount outstanding	$ 249,000,000
Fixed charge coverage ratio	142.00%
Leverage ratio	267.00%
Number of interest rate swaps \| agreement	2
Fair value (liability) of interest rate swaps	$ (800,000)
Fair value of long term asset	400,000
Fair value of current liability	$ 1,200,000
Debt maturity date	Aug. 29, 2019
PNC Bank [Member]
Debt Instrument [Line Items]
Closing costs of debt	$ 6,900,000
Loan initiation amortization period	5 years
Minimum [Member]
Debt Instrument [Line Items]
Fixed charge coverage ratio	125.00%
Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio	275.00%
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	3.50%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	$ 110,000,000
Revolving Credit Facility [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	250,000,000
Term Loan [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	139,000,000
Term Loan [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Debt face amount	$ 175,000,000
Sunrise Coal [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Percentage decrease in amount of debt with maximum interest rate per quarter after commencement date	10.00%
Date that the percentage of debt with a maximum interest rate begins to decrease quarterly	Mar. 31, 2016
Sunrise Coal [Member] \| Maximum [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Interest rate maximum	5.00%
Sunrise Coal [Member] \| Revolving Credit Facility [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Amount of debt with maximum interest rate	$ 100,000,000
Sunrise Coal [Member] \| Term Loan [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Amount of debt with maximum interest rate	$ 175,000,000

Amount of debt with maximum interest rate

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Fixed charge coverage ratio

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Percentage decrease in amount of debt with maximum interest rate

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The net increase(decrease) in interest income during the period representing the allocation of deferred loan origination fees less deferred loan origination costs using the effective interest method over the term of the debt arrangement to which they pertain taking into account the effect of prepayments.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Face (par) amount of debt instrument at time of issuance.

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Maximum contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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Fair value as of the balance sheet date of interest rate derivative assets, net of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized on the balance sheet.

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Fair value of the amount outstanding under the credit facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Number of interest rate derivative instruments held by the entity at the reporting date.

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