Sale and Exchange of Properties (Details) (USD $)	0 Months Ended	3 Months Ended	6 Months Ended		0 Months Ended
	May 07, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 16, 2014 Nora Gathering, LLC	Jun. 16, 2014 Range acre item
Exchange of Properties
Approximate area of acquisition (in acres)					73,000
Number of producing wells acquired					900
Area of property transferred under the asset exchange agreement (in acres)					138,000
Number of producing wells transferred under the asset exchange agreement					2,000
Ownership interest transferred (as a percent)					50.00%
Amount of cash, subject to certain post-closing adjustments	$ 157,300,000		$ 157,256,000		$ 157,300,000
Ownership percentage				50.00%
Fair value of the consideration acquired					510,300,000
Pre-tax gain recorded					37,700,000
Pre-tax gain on de-designation of derivative instruments		$ 28,000,000	$ 28,000,000		$ 28,000,000