Properties and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment
Proved Natural Gas and Crude Oil Properties	$ 1,976,930	$ 1,677,271
Unproved Natural Gas and Crude Oil Properties	288,208	253,464
Total Natural Gas and Crude Oil Properties	2,265,138	1,930,735
Equipment and other	30,428	28,832
Land and Buildings	12,668	13,434
Construction in Progress	146,324	41,180
Properties and equipment, at cost	2,454,558	2,014,181
Accumulated DD&A	(670,761)	(529,543)
Property, Plant and Equipment, Net	$ 1,783,797	$ 1,484,638