Accounting Changes and Error Corrections Accountings Changes and Error Corrections (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Income Statement [Abstract]
Oil and gas sales	$ 133,896	$ 152,981	$ 441,440	$ 442,015
Total Revenues	138,794	150,933	438,968	441,301
Depreciation, Depletion and Amortization	65,331	67,274	201,072	187,503
Lease operating cost	22,067	23,078	70,606	76,919
Transportation and gas processing	5,107	5,783	16,412	15,386
Severance and other taxes	10,191	11,695	28,829	32,221
Total Costs and Expenses	133,319	137,949	410,025	403,120
Income Before Income Taxes	5,475	12,984	28,943	38,181
Provision for Income Taxes	3,001	5,625	14,200	15,235
Net Income	2,474	7,359	14,743	22,946	(2,442)
Earnings Per Share, Basic	$ 0.06	$ 0.17	$ 0.34	$ 0.53
Earnings Per Share, Diluted	$ 0.06	$ 0.17	$ 0.33	$ 0.53
Statement of Cash Flows [Abstract]
Deferred income taxes			13,507	15,235
Other Noncash Income (Expense)			(390)	(4,093)
(Increase) Decrease in accounts receivable			14,159	(3,293)
Increase (decrease) in accounts payable and accrued liabilities			7,299	2,588
Net Cash Provided by Operating Activities			252,175	225,607
Scenario, Previously Reported [Member]
Income Statement [Abstract]
Oil and gas sales		155,049		442,418
Total Revenues		153,001		441,704
Depreciation, Depletion and Amortization		66,948		186,526
Lease operating cost		23,078		77,459
Transportation and gas processing		5,783		16,678
Severance and other taxes		11,695		31,971
Total Costs and Expenses		137,623		403,725
Income Before Income Taxes		15,378		37,979
Provision for Income Taxes		6,492		15,162
Net Income		8,886		22,817
Earnings Per Share, Basic		$ 0.20		$ 0.53
Earnings Per Share, Diluted		$ 0.20		$ 0.52
Statement of Cash Flows [Abstract]
Deferred income taxes				15,162
Other Noncash Income (Expense)				(3,796)
(Increase) Decrease in accounts receivable				(3,696)
Increase (decrease) in accounts payable and accrued liabilities				3,873
Net Cash Provided by Operating Activities				225,607
Restatement Adjustment [Member]
Income Statement [Abstract]
Oil and gas sales		(2,068)		(403)
Total Revenues		(2,068)		(403)
Depreciation, Depletion and Amortization		326		977
Lease operating cost		0		(540)
Transportation and gas processing		0		(1,292)
Severance and other taxes		0		250
Total Costs and Expenses		326		(605)
Income Before Income Taxes		(2,394)		202
Provision for Income Taxes		(867)		73
Net Income		(1,527)		129
Earnings Per Share, Basic		$ (0.03)		$ 0.00
Earnings Per Share, Diluted		$ (0.03)		$ 0.01
Statement of Cash Flows [Abstract]
Deferred income taxes				73
Other Noncash Income (Expense)				(297)
(Increase) Decrease in accounts receivable				403
Increase (decrease) in accounts payable and accrued liabilities				(1,285)
Net Cash Provided by Operating Activities				$ 0