Acquisitions (Details) (Chesapeake, USD $) In Millions, unless otherwise specified	0 Months Ended
	Jun. 03, 2013 acre
Acquisitions
Approximate area of acquisition (in acres)	99,000
Purchase price of acquisition	$ 114.6
Purchase price of acquisition allocated to undeveloped acreage	56.7
Marcellus
Acquisitions
Approximate area of acquisition (in acres)	67,000
Number of wells acquired	10
Purchase price of acquisition allocated to acquired wells	$ 57.9
Portion unlikely to be developed (in acres)	42,000
Expected increase in sales volume (in Bcfe)	2,000
Acquisition of proved developed reserves (Bcfe)	54,000