Income Taxes (Schedule of Tax Effect of Temporary Differences) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value of Commodity Derivative Instruments	$ 3,865	$ 175
Prepaid Assets	(1,779)	(1,435)
Accruals and Other	1,236	(1,563)
Net current deferred tax asset (liability)	3,322	(2,823)
Restricted stock awards and options	2,313	1,272
Federal and state net operating loss carryforwards	60,406	60,266
Fair value opf commodity derivative instruments		71
Percentage depletion carryforward	4,211	4,105
Other Noncurrent Deferred Tax Asset	57	943
Non-current deferred tax asset	66,987	66,657
Property, plant and equipment, principally due to differences in depreciation	(134,681)	(98,432)
Net non-current deferred tax liability	(67,694)	(31,775)
Parent Company [Member]
Net non-current deferred tax liability	$ (59,571)	$ (23,831)