Derivative Instruments (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 MMcf	Jun. 30, 2012	Jun. 30, 2013 MMcf	Jun. 30, 2012	Dec. 31, 2012 MMcf
Natural Gas Hedging Instruments
Absolute quantities of derivative commodity instruments that have been designated and qualify as cash flow hedges (in Bcf)	414,000		414,000		365,000
Absolute quantities of the derivative commodity instruments that have been designated and qualify as fair value hedges (in Bcf)	5,000		5,000		8,000
Deferred net gains in accumulated other comprehensive income (loss), net of tax	$ 122,700,000		$ 122,700,000		$ 138,200,000
Net unrealized gains on derivative commodity instruments	71,700,000		71,700,000
Reduction in operating revenue	(520,092,000)	(337,804,000)	(1,078,752,000)	(787,764,000)
Increase of accumulated other comprehensive income	63,411,000	(70,333,000)	(14,554,000)	(7,446,000)
Margin deposits remitted by brokers with company	0		0		0
Margin deposits with brokers	700,000		700,000		700,000
Additional collateral limit for below investment grade derivative instruments, as a percentage of the derivative liability			100.00%
Aggregate fair value of derivative instruments with credit-risk related contingencies	900,000		900,000
Collateral posted	0		0
Additional collateral for downgrade below investment grade	700,000		700,000
EQT Production segment
Natural Gas Hedging Instruments
Reduction in operating revenue	(306,132,000)	(158,649,000)	(556,643,000)	(354,045,000)
Correction of error related to the accounting for a derivative instrument put premium
Natural Gas Hedging Instruments
Increase of accumulated other comprehensive income		5,100,000
Deferred income taxes		3,100,000
Correction of error related to the accounting for a derivative instrument put premium | EQT Production segment
Natural Gas Hedging Instruments
Reduction in operating revenue		8,200,000
Commodity contracts
Natural Gas Hedging Instruments
Margin deposits with brokers	656,000		656,000		736,000
Commodity derivatives designated as cash flow hedges | Interest rate swaps settled
Derivatives designated as hedging instruments
Amount of gain (loss) recognized in OCI (effective portion), net of tax		(6,670,000)		(4,297,000)
Amount of gain (loss) reclassified from accumulated OCI into operating revenues (effective portion), net of tax	(36,000)	(64,000)	(72,000)	(129,000)
Commodity derivatives designated as cash flow hedges | Commodity contracts
Derivatives designated as hedging instruments
Amount of gain (loss) recognized in OCI (effective portion), net of tax	73,429,000	(8,930,000)	20,828,000	98,558,000
Amount of gain (loss) reclassified from accumulated OCI into operating revenues (effective portion), net of tax	10,490,000	55,286,000	36,323,000	103,272,000
Amount of loss recognized in operating revenues (ineffective portion)	(7,473,000)	(212,000)	(7,954,000)	(243,000)
Derivatives not designated as hedging instruments:
Amount of gain (loss) recognized in operating revenues	1,512,000	(790,000)	1,250,000	1,673,000
Commodity derivatives designated as fair value hedges | Commodity contracts
Derivatives designated as hedging instruments
Amount of gain (loss) recognized in operating revenues for fair value commodity contracts	2,700,000	(2,378,000)	(839,000)	4,694,000
Fair value (loss) gain recognized in operating revenues for inventory designated as hedged item	(4,075,000)	8,388,000	462,000	(1,543,000)
Derivatives not designated as hedging instruments:
Amount of gain (loss) recognized in income due to exclusion of the spot/forward differential from the assessment of effectiveness	800,000	6,000,000	2,100,000	2,800,000
Amount of gain (loss) recognized in income due to changes in basis	$ (2,200,000)		$ (2,500,000)	$ (400,000)