EQT Midstream Partners, LP (Details)								3 Months Ended	9 Months Ended
	Oct. 22, 2015 USD ($) shares	Oct. 20, 2015 $ / shares	May. 15, 2015	Mar. 30, 2015 USD ($) mi Bcf	Mar. 18, 2015 shares	Mar. 17, 2015 USD ($) shares	Feb. 17, 2015	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Apr. 15, 2015 USD ($)	Jul. 31, 2012 shares
Subsidiary or equity method investee
Proceeds from offerings									$ 758,812,000	$ 902,467,000
General partner's interest (as a percent)								2.00%
Increase to deferred tax liability						$ 73,000,000		$ 5,400,000
Common Stock
Subsidiary or equity method investee
Increase (Decrease) in additional paid in capital, change in subsidiary ownership						122,800,000		9,200,000
Noncontrolling Interests in Consolidated Subsidiaries
Subsidiary or equity method investee
Increase (Decrease) in additional paid in capital, change in subsidiary ownership						$ (195,800,000)		(14,600,000)
Limited Partner Common
Subsidiary or equity method investee
Number of common units issued to the public in an offering (in shares) | shares					1,237,500
Ownership interest (as a percent)			90.10%
EQT Energy Supply, LLC
Subsidiary or equity method investee
Total consideration											$ 124,300,000
MVP Interest in Joint Venture
Subsidiary or equity method investee
Consideration				$ 54,200,000
Capital contributions made by the company (as a percent)				100.00%
Firms Capacity Commitments Per Day | Bcf				2.0
Duration of Firm Capacity Commitments				20 years
EQT Midstream Partners LP
Subsidiary or equity method investee
Number of subordinated units (in shares) | shares												17,339,718
Conversion ratio							1
Number of common units issued to the public in an offering (in shares) | shares						8,250,000
Proceeds from offerings						$ 696,600,000		62,200,000
Underwriters discount and offering expenses						24,500,000		500,000
Common unit aggregate offering price, maximum amount (in dollars per share)								$ 750,000,000
Common units issued (in shares) | shares								827,975
Common unit, issued, average price per unit (in dollars per share) | $ / shares								$ 76.58
Payments for commissions								$ 700,000
EQT Midstream Partners LP | Subsequent Event
Subsidiary or equity method investee
Cash distribution declared	$ 28,600,000
EQT Midstream Partners LP | General Partner | Subsequent Event
Subsidiary or equity method investee
Cash distribution declared (in dollars per share) | $ / shares		$ 0.675
Common unit, outstanding | shares	71,870,181
Cash distribution declared	$ 1,200,000
Cash distribution declared related to IDRs	12,700,000
EQT Midstream Partners LP | Limited Partner [Member] | Subsequent Event
Subsidiary or equity method investee
Cash distribution declared	$ 14,700,000
EQT Midstream Partners LP | Northern West Virginia Marcellus Gathering System
Subsidiary or equity method investee
Consideration						925,700,000
Cash consideration						$ 873,200,000
EQT Midstream Partners LP | Northern West Virginia Marcellus Gathering System | Partnership Interest | Common Partner Units
Subsidiary or equity method investee
Number of common units representing limited partner interest (in shares) | shares						511,973
EQT Midstream Partners LP | Northern West Virginia Marcellus Gathering System | Partnership Interest | General Partner Units
Subsidiary or equity method investee
Number of common units representing limited partner interest (in shares) | shares						178,816
EQT Midstream Partners LP | MVP Holdco
Subsidiary or equity method investee
Ownership interest (as a percent)				100.00%
Mountain Valley Pipeline
Subsidiary or equity method investee
Length of natural gas interstate pipeline (in miles) | mi				300
EQT Corporation and Subsidiaries | MVP Interest in Joint Venture
Subsidiary or equity method investee
Firms Capacity Commitments Per Day | Bcf				1.3