Summary of Significant Accounting Policies (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
EQT Midstream
Property Net Revenue and Operating Expense
Total regulated net revenues	$ 184,767	$ 131,184	$ 113,774
Total regulated operating expenses	$ 71,517	$ 66,202	$ 76,247
Gathering and transmission systems | Minimum
Property, Plant and Equipment:
Estimated service life	25 years
Gathering and transmission systems | Maximum
Property, Plant and Equipment:
Estimated service life	60 years
Building
Property, Plant and Equipment:
Estimated service life	35 years
Office equipment | Minimum
Property, Plant and Equipment:
Estimated service life	3 years
Office equipment | Maximum
Property, Plant and Equipment:
Estimated service life	7 years
Vehicles
Property, Plant and Equipment:
Estimated service life	5 years
Computer and telecommunications equipment and systems | Minimum
Property, Plant and Equipment:
Estimated service life	3 years
Computer and telecommunications equipment and systems | Maximum
Property, Plant and Equipment:
Estimated service life	7 years