EQT Midstream Partners, LP (Details) (USD $)	0 Months Ended	9 Months Ended	3 Months Ended		0 Months Ended		0 Months Ended
	Jul. 02, 2012	Sep. 30, 2012	Sep. 30, 2012 Performance awards	Sep. 30, 2012 Phantom units	Jul. 02, 2012 Line of credit	Jul. 02, 2012 Equitrans	Jul. 02, 2012 EQT Midstream Partners
Subsidiary or equity method investee
Number of common units issued to the public in an offering (in shares)							14,375,000
Common units issued to the public in an offering as a percentage of outstanding equity							40.60%
Ownership percentage	59.40%	59.40%
Common units (in shares)	2,964,718
Subordinated units (in shares)	17,339,718
General partner's interest (as a percent)							2.00%
Percentage of ownership contributed						100.00%
Additional borrowing					$ 350,000,000
Reversal of net deferred tax liability		5,371,000
Number of shares granted			146,490	4,780
Cash received, net of issuance costs, upon closing of the IPO							277,000,000
Portion of proceeds from IPO that are distributed to parent							231,000,000
Amount retained to replenish amounts distributed by Equitrans to EQT							12,000,000
Amount retained to pre-fund maintenance capital expenditures							32,000,000
Payment of revolving credit facility origination fees		$ 4,022,000					$ 2,000,000