Bank Debt (Details)	9 Months Ended
Sep. 30, 2015 USD ($)
Debt Instrument [Line Items]
Maximum leverage ratio	350.00%
Leverage ratio	258.00%
Debt maturity date	Aug. 29, 2019
Interest rat swaps net fair value	$ 2,500,000
PNC Bank [Member]
Debt Instrument [Line Items]
Closing costs of debt	$ 6,800,000
Loan initiation amortization period	5 years
Credit agreement, amount outstanding	$ 266,000,000
Credit facility, maximum borrowing capacity	311,000,000
Revolving Credit Facility [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	120,000,000
Credit facility, maximum borrowing capacity	$ 250,000,000
Term Loan [Member] \| Debt Instrument, Redemption, Period Five [Member]
Debt Instrument [Line Items]
Loan annual amortization	20.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period Four [Member]
Debt Instrument [Line Items]
Loan annual amortization	20.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument [Line Items]
Loan annual amortization	10.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument [Line Items]
Loan annual amortization	15.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Loan annual amortization	15.00%
Term Loan [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	$ 146,000,000
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
Leverage Ratio Less Than 1 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	2.25%
Leverage Ratio Between 1 and 1.5 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	2.50%
Leverage Ratio Between 1.5 and 2 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	2.75%
Leverage Ratio Between 2 and 2.5 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	3.00%
Leverage Ratio Above 2.5 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	3.50%

Amount of debt with maximum interest rate

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Leverage Ratio

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Loan Initiation Amortization Period - Years

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Maximum leverage 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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- Definition

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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- Definition

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

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- Definition

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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- Definition

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

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Fair value of all derivatives designated as interest rate fair value hedging instruments.

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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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