Acquisitions - Fair Value of Assets Acquired (Details) (Utica Shale [Member], USD $) In Thousands, unless otherwise specified	0 Months Ended	12 Months Ended
	Mar. 20, 2014	Dec. 31, 2014	Mar. 20, 2014
Business Acquisition [Line Items]
Cash, net of purchase price adjustments	$ 179,527	$ 179,500
Fair value of net identifiable assets acquired	179,527		179,527
Proved Properties [Member]
Business Acquisition [Line Items]
Fair value of net identifiable assets acquired	31,961		31,961
Unproved Properties [Member]
Business Acquisition [Line Items]
Fair value of net identifiable assets acquired	6,263		6,263
Unevaluated Properties [Member]
Business Acquisition [Line Items]
Fair value of net identifiable assets acquired	$ 141,303		$ 141,303