Accounting Changes and Error Corrections Accounting Changes and Error Corrections (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Statement of Financial Position [Abstract]
Accounts receivable	$ 70,897		$ 71,203
Deferred tax asset	10,715		8,262
Total Current Assets	92,489		87,005
Accumulated depreciation, depletion, and amortization	(3,125,282)		(2,824,839)
Property and Equipment, Net	2,588,817		2,367,954
Total Assets	2,698,505		2,473,463
Accounts payable and accrued liabilities	82,318		77,310
Total Current Liabilities	176,033		179,412
Deferred Tax Liabilities	241,205		234,493
Other Long-Term Liabilities	10,324		10,198
Additional paid-in capital	762,242		748,517
Retained earnings	315,244		317,686
Total Stockholders' Equity	1,065,350		1,052,783
Total Liabilities and Stockholders' Equity	2,698,505		2,473,463
Income Statement [Abstract]
Oil and gas sales	585,229		558,390		601,019
Total Revenues	584,401		561,486		597,809
General and administrative, net	45,423		47,097		45,325
Depreciation, Depletion and Amortization	252,769		249,344		223,081
Lease operating cost	99,731		97,835		89,069
Transportation and gas processing	21,044		19,467		15,722
Severance and other taxes	42,725		47,546		53,351
Write-down of oil and gas properties	46,948		0		0
Total Costs and Expenses	584,203		523,713		466,684
Income from Continuing Operations Before Income Taxes	198		37,773		131,125
Provision (Benefit) for Income Taxes	2,640		16,072		49,054
Income from Continuing Operations	(2,442)		21,701		82,071
Net Income (Loss)	(2,442)		21,701		96,282
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.06)		$ 0.51		$ 1.94
Earnings Per Share, Basic	$ (0.06)		$ 0.51		$ 2.27
Income (Loss) from Continuing Operations, Per Diluted Share	$ (0.06)		$ 0.50		$ 1.91
Earnings Per Share, Diluted	$ (0.06)		$ 0.50		$ 2.24
Statement of Comprehensive Income [Abstract]
Comprehensive Income	(2,442)		21,701		96,420
Statement of Cash Flows [Abstract]
Deferred income taxes	2,647		17,231		47,555
Share-based compensation expenses	10,099		13,795		12,955
Other	(5,443)		976		2,143
Increase (Decrease) in Accounts Receivable	(1,894)		(1,534)		(11,303)
Increase (Decrease) in Accounts Payable and Accrued Liabilities	2,607		(1,013)		10,610
Net Cash Provided by (Used in) Operating Activities	311,447		314,606		373,058
Scenario, Previously Reported [Member]
Statement of Financial Position [Abstract]
Accounts receivable	70,897		67,318
Deferred tax asset	4,974		5,679
Total Current Assets	86,748		80,537
Accumulated depreciation, depletion, and amortization	(3,174,453)		(2,847,773)
Property and Equipment, Net	2,539,646		2,345,020
Total Assets	2,643,593		2,444,061
Accounts payable and accrued liabilities	83,361		75,378
Total Current Liabilities	177,076		177,480
Deferred Tax Liabilities	217,384		223,243
Other Long-Term Liabilities	10,324		9,901
Additional paid-in capital	761,972		747,868
Retained earnings	283,380		302,412
Total Stockholders' Equity	1,033,216		1,036,860
Total Liabilities and Stockholders' Equity	2,643,593		2,444,061
Income Statement [Abstract]
Oil and gas sales	588,541		554,194		602,341
Total Revenues	587,713		557,290		599,131
General and administrative, net	45,802		46,778		45,362
Depreciation, Depletion and Amortization	252,043		247,178		221,230
Lease operating cost	101,611		97,295
Transportation and gas processing	22,336		18,175
Severance and other taxes	42,252		48,862		52,508
Write-down of oil and gas properties	73,911
Total Costs and Expenses	613,518		520,712		464,027
Income from Continuing Operations Before Income Taxes	(25,805)		36,578		135,104
Provision (Benefit) for Income Taxes	(6,773)		15,639		50,494
Income from Continuing Operations	(19,032)		20,939		84,610
Net Income (Loss)	(19,032)		20,939		98,821
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.44)		$ 0.49		$ 2.00
Earnings Per Share, Basic	$ (0.44)		$ 0.49		$ 2.33
Income (Loss) from Continuing Operations, Per Diluted Share	$ (0.44)		$ 0.48		$ 1.97
Earnings Per Share, Diluted	$ (0.44)		$ 0.48		$ 2.30
Statement of Comprehensive Income [Abstract]
Comprehensive Income	(19,032)		20,939		98,959
Statement of Cash Flows [Abstract]
Deferred income taxes	(6,766)		16,798		48,995
Share-based compensation expenses	10,478		13,476		12,625
Other	(5,146)
Increase (Decrease) in Accounts Receivable	(5,779)		3,235		(12,625)
Increase (Decrease) in Accounts Payable and Accrued Liabilities	5,582		(2,102)		10,134
Net Cash Provided by (Used in) Operating Activities	311,447		314,606		373,058
Restatement Adjustment [Member]
Statement of Financial Position [Abstract]
Accounts receivable	0		3,885	[1]
Deferred tax asset	5,741		2,583
Total Current Assets	5,741		6,468
Accumulated depreciation, depletion, and amortization	49,171		22,934	[2]
Property and Equipment, Net	49,171		22,934
Total Assets	54,912		29,402
Accounts payable and accrued liabilities	(1,043)		1,932
Total Current Liabilities	(1,043)		1,932
Deferred Tax Liabilities	23,821		11,250	[2]
Other Long-Term Liabilities	0		297
Additional paid-in capital	270		649
Retained earnings	31,864		15,274	[2]
Total Stockholders' Equity	32,134		15,923
Total Liabilities and Stockholders' Equity	54,912		29,402
Income Statement [Abstract]
Oil and gas sales	(3,312)	[1]	4,196	[1]	(1,322)
Total Revenues	(3,312)		4,196		(1,322)
General and administrative, net	(379)		319		(37)
Depreciation, Depletion and Amortization	726		2,166		1,851
Lease operating cost	(1,880)		540
Transportation and gas processing	(1,292)		1,292
Severance and other taxes	473		(1,316)		843
Write-down of oil and gas properties	(26,963)
Total Costs and Expenses	(29,315)		3,001		2,657
Income from Continuing Operations Before Income Taxes	26,003		1,195		(3,979)
Provision (Benefit) for Income Taxes	9,413		433		(1,440)
Income from Continuing Operations	16,590		762		(2,539)
Net Income (Loss)	16,590		762		(2,539)
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.38		$ 0.02		$ (0.06)
Earnings Per Share, Basic	$ 0.38		$ 0.02		$ (0.06)
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.38		$ 0.02		$ (0.06)
Earnings Per Share, Diluted	$ 0.38		$ 0.02		$ (0.06)
Statement of Comprehensive Income [Abstract]
Comprehensive Income	16,590		762		(2,539)
Statement of Cash Flows [Abstract]
Deferred income taxes	9,413		433		(1,440)
Share-based compensation expenses	(379)		319		330
Other	(297)
Increase (Decrease) in Accounts Receivable	3,885		(4,769)		1,322
Increase (Decrease) in Accounts Payable and Accrued Liabilities	(2,975)		1,089		476
Net Cash Provided by (Used in) Operating Activities	$ 0		$ 0		$ 0

[1] The adjustments column includes the impact of a $2.9 million revenue adjustment related to the 2012 finalization of a property unitization which was originally recorded in 2013.

[2] 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.