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The noncash expense charged against earnings to recognize the consumption of natural resources.

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-Publisher FASB

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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This element represents the applicable amount of income taxes or benefit realized on the gain (loss) on sale of properties during the reporting period.

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-Publisher SEC

-Name Regulation S-X (SX)

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Amount of the difference between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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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 nondeductible depletion.

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The tax effect of gains or losses resulting from material events or transactions (that would not reasonably be expected to recur in the foreseeable future) that possesses a high degree of abnormality and are clearly unrelated to, or incidentally related to, the ordinary and typical activities of the entity.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Income Taxes Income Tax Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014 Rate	Sep. 30, 2013 Rate	Mar. 31, 2009 Internal Revenue Service (IRS) [Member]	Mar. 31, 2008 Internal Revenue Service (IRS) [Member]	Sep. 30, 2014 Internal Revenue Service (IRS) [Member]	Sep. 30, 2013 Potomac coal reserves [Member]	Sep. 30, 2013 Crowsnest Pass [Member]
Reconciliation of Statutory Federal Tax Rate [Line Items]
Effective Income Tax Rate Reconciliation, Percent	8.30%	323.00%
Amount
Unusual or Infrequent, Tax Effect	$ 7,013				$ 8,820
Depletion	7,970		2,925	4,493
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount	957	5,875	1,402
Income Tax Reconciliation, Nondeductible Expense, Depletion	20,640	111,104
Percent
Statutory U.S. Federal Income Tax Rate	35.00%	35.00%
Gain (Loss) on Sale of Properties, Applicable Income Taxes						$ 4,701	$ 8,467