Financial Statements (Details)	1 Months Ended
	Jul. 31, 2012	Jul. 02, 2012
Equitrans
Summary of Significant Accounting Policies
Percentage of ownership contributed		100.00%
EQT Midstream Partners
Summary of Significant Accounting Policies
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%
Common units (in shares)		2,964,718
Subordinated units (in shares)		17,339,718
General partner's interest (as a percent)	2.00%