Commitments and Contingencies Commitments and Contingencies (Details)	9 Months Ended
	Sep. 30, 2015 USD ($) $ / MMBTU
CONSOL Carried Cost Obligation [Member]
Other Commitments [Line Items]
Equity method investment, ownership percentage	50.00%
Maximum amount to be paid each calendar year for funding of future drilling and completion costs	$ 400,000,000
Funding of joint venture's future drilling and completion costs	$ 1,600,000,000
Natural gas price agreed upon benchmark, average	4.00
Consent Decree [Member]
Other Commitments [Line Items]
Civil penalty	$ 4,950,000
Mitigation projects	4,500,000
Supplemental environmental projects	$ 4,000,000