Discontinued Operations (Details) - Buchanan and Other Assets [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Coal Revenue	$ 303,707	$ 620,155
Other Outside Sales	14,856	27,742
Freight-Outside Coal	17,763	30,045
Miscellaneous Other Income	8,934	26,330
Gain on Sale of Assets	5,581	13,536
Total Revenue and Other Income	350,841	717,808
Total Costs	289,790	605,620
Income From Operations Before Income Taxes	61,051	112,188
Income Tax Expense	9,035	2,668
Less: Net Income Attributable to Noncontrolling Interest	4,313	9,777
Income From Discontinued Operations, net	$ 47,703	$ 99,743

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