Natural Gas Producing Activities (Unaudited) - Costs Incurred Relating to Natural Gas, NGL, and Oil Production Activities (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capitalized Costs:
Proved properties		$ 10,918,499	$ 9,258,298	$ 7,702,724
Unproved properties		898,270	824,527	450,227
Total capitalized costs		11,816,769	10,082,825	8,152,951
Accumulated depreciation and depletion		3,425,618	2,693,535	2,134,953
Net capitalized costs		8,391,151	7,389,290	6,017,998
Property acquisition:
Proved properties		23,890	231,322	90,390
Unproved properties		158,405	493,067	95,861
Exploration		53,463	16,023	4,285
Development		$ 1,633,498	1,697,501	1,230,301
Chesapeake
Property acquisition:
Unproved properties	$ 57,200
Permian | Range Resources Corporation
Property acquisition:
Unproved properties			317,200
Proved properties, wells			198,200
Proved properties, leases			$ 1,100
Marcellus | Chesapeake
Property acquisition:
Proved properties	$ 57,000
Unproved properties				41,900
Proved properties, wells				57,000
Proved properties, leases				$ 15,300