Sales of Properties and Contracts (Details) a in Thousands, MMcf in Thousands, $ in Thousands		1 Months Ended	12 Months Ended
	Dec. 31, 2013 USD ($) customer	Jun. 30, 2014 USD ($) a well	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) customer MMcf	Dec. 17, 2013 USD ($) customer
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of energy marketing contracts in cash			$ 0	$ 0	$ 23,000
Pre-tax gain recorded			$ 0	34,146	19,618
Pre-tax gain on de-designation of derivative instruments		$ 28,000
Nora Gathering, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage		50.00%
EQT Production
Schedule of Equity Method Investments [Line Items]
Pre-tax gain recorded				27,400
Range Resources Corporation
Schedule of Equity Method Investments [Line Items]
Approximate area of acquisition (in acres) | a		73
Number of producing wells acquired | well		900
Area of property transferred under asset exchange agreement (in acres) | a		138
Number of producing wells transferred under asset exchange agreement | well		2,000
Ownership interest transferred		50.00%
Fair value of assets		$ 516,500
Pre-tax gain recorded		34,100
Range Resources Corporation | Acreage
Schedule of Equity Method Investments [Line Items]
Fair value of assets		318,300
Range Resources Corporation | Wells
Schedule of Equity Method Investments [Line Items]
Fair value of assets		198,200
Range Resources Corporation | EQT Production
Schedule of Equity Method Investments [Line Items]
Amount of cash, subject to certain post-closing adjustments		$ 167,300
Equitable Gas and Homeworks
Schedule of Equity Method Investments [Line Items]
Sale of energy marketing contracts					$ 20,000
Number of customers with whom natural gas sale agreements are entered | customer	1,000				1,000
Sale volumes of energy marketing contracts (in MMcf) | MMcf					12
Proceeds from sale of energy marketing contracts in cash	$ 18,000
Amount expected to be collected				$ 2,000
Gain on sale of energy marketing contracts					$ 19,600
Number of customers with whom natural gas sale agreements are entered related to certain acquired assets | customer						50
Value of energy marketing contracts						$ 5,000
Sale of energy marketing contracts related to certain acquired assets	$ 5,000				$ 5,000