Income Taxes (Schedule of Tax Effect of Temporary Differences) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Federal and state net operating loss carryforwards	$ 62,015	$ 62,130
Fair Value of Commodity Derivative Instruments	11,578	3,912
Restricted stock awards and options	3,843	2,313
Percentage depletion carryforward	5,003	4,575
Accruals and Other	1,130	2,613
Deferred Tax Assets	83,569	75,543
Property, plant and equipment, principally due to differences in depreciation	193,191	136,016
Deferred Tax Liabilities, Derivatives	182	214
Prepaid Assets	1,482	1,778
Deferred Tax Liabilities, Other	2,577	1,907
Deferred tax liabilities	197,432	139,915
Total deferred tax Liabilities	113,863	64,372
Deferred tax asset	8,949	3,322
Deferred tax liabilities	122,812	67,694
Parent Company [Member]
Deferred tax asset	8,949	3,322
Deferred tax liabilities	$ 106,910	$ 59,571