Summary of Significant Accounting Policies (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011
Summary of Significant Accounting Policies
Equity method ownership percentage	50.00%
Number of reportable segments	2
Cash Equivalents:
Maximum original term of maturity for investments to be classified as cash or cash equivalents	3 months
Inventories:
Losses recorded for lower of cost or market adjustments	$ 400,000	$ 7,000,000	$ 7,200,000
Oil and gas producing properties, successful efforts method	8,152,951,000	6,750,343,000	5,772,083,000
Accumulated depletion	(2,134,953,000)	(1,572,775,000)	(1,177,526,000)
Net capitalized costs	6,017,998,000	5,177,568,000	4,594,557,000
Property, Plant and Equipment:
Property, plant and equipment	11,062,136,000	9,153,207,000
Accumulated depreciation and amortization	(2,728,374,000)	(2,093,795,000)
Net property, plant and equipment	8,333,762,000	7,059,412,000
Capitalized internal costs of oil and gas producing properties under the successful efforts method	93,500,000	72,100,000	69,300,000
Capitalized interest costs	22,900,000	15,600,000	13,300,000
Depletion rate of oil and gas producing properties under successful efforts method (in dollars per Mcfe)	1.50	1.52	1.25
Capitalized costs of undeveloped properties	450,200,000	385,600,000
Undeveloped property impairments	14,200,000	5,500,000	2,600,000
Deferred taxes related to regulatory assets	13,300,000	18,300,000
EQT Midstream
Property, Plant and Equipment:
Property, plant and equipment	2,807,165,000	2,308,362,000
Accumulated depreciation and amortization	(547,991,000)	(483,358,000)
Net property, plant and equipment	2,259,174,000	1,825,004,000
Other Properties
Property, Plant and Equipment:
Net property, plant and equipment	$ 56,590,000	$ 56,840,000