Summary of Significant Accounting Policies (Details Textual) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) shares	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) $ / MMBTU $ / bbl	Dec. 31, 2014 USD ($)	Sep. 30, 2014 $ / MMBTU $ / BBL
Derivative [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares	2,351,557				2,400,000
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Debt Issuance Cost								$ 1,800
Long-term Line of Credit	$ 0				$ 0		$ 0
Senior unsecured notes	390,959				390,959		390,959	0
Capitalized general and administrative costs	1,400			$ 1,500	4,900	$ 4,300
Capitalized interest expense	500			800	$ 2,900	2,200
Present value discounted percent of future net revenues of proved oil and natural gas reserves					10.00%
Net capitalized costs less related deferred income taxes exceeded the full-cost ceiling		$ 146,300	$ 42,800		$ 252,400
Impairment of Oil and Gas Properties	285,721	229,000	67,100	$ 0	581,874	$ 0
Deferred income tax credit	33,300	$ 82,700	$ 24,300		140,300
Assets held for sale	32,413				32,413		$ 32,413	$ 0
Oil
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Average oil and natural gas prices							55.73		95.56
Natural Gas
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Average oil and natural gas prices | $ / MMBTU							3.06		4.24
Revolving Credit Facility
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Deferred Finance Costs Disclosures	1,100				1,100		$ 1,100
Senior Unsecured Notes
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Deferred Finance Costs Disclosures	$ 9,000				$ 9,000		$ 9,000
Restricted Stock Units (RSUs)
Derivative [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares	73,630				73,630
Preferred Stock
Derivative [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares	0				1,500,000
Restricted Stock
Derivative [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares	823,832				823,832