Accounting Changes and Error Corrections Accounting Changes and Error Corrections (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended										12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Restatement Adjustment [Member]	Dec. 31, 2012 Restatement Adjustment [Member]		Dec. 31, 2011 Restatement Adjustment [Member]	Dec. 31, 2013 Ceiling Test Calculation Error Correction [Member] Restatement Adjustment [Member]	Dec. 31, 2012 Ceiling Test Calculation Error Correction [Member] Restatement Adjustment [Member]	Dec. 31, 2008 Ceiling Test Calculation Error Correction [Member] Restatement Adjustment [Member]	Dec. 31, 2012 Property Unitization Error Correction [Member] Restatement Adjustment [Member]
Property and Equipment, Net	$ 2,588,817	$ 2,367,954		$ 49,171	$ 22,934			$ 49,000
Deferred Tax Liabilities, Net	394,525	367,251						18,000	9,000
Retained earnings	315,244	317,686		31,864	15,274	[1]		31,000	15,000	15,000
Impairment of Oil and Gas Properties	46,948	0	0	(26,963)				27,000
Depreciation, Depletion and Amortization	252,769	249,344	223,081	726	2,166		1,851	1,000	23,000
Net Income (Loss)	(2,442)	21,701	96,282	16,590	762		(2,539)	16,000
Provision (Benefit) for Income Taxes	2,640	16,072	49,054	9,413	433		(1,440)	9,000
Total Revenues	$ 584,401	$ 561,486	$ 597,809	$ (3,312)	$ 4,196		$ (1,322)				$ 2,900

[1] The adjustments column includes the impact of correcting the error in the ceiling test write-down as of December 31, 2012. Included in these amounts are approximately $23 million related to Accumulated depreciation, depletion, and amortization, $9 million related to the net deferred tax liabilities and $15 million related to retained earnings.