Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property, Plant and Equipment:
Composite rate of depreciation for distribution property, plant and equipment (as a percent)	4.00%	4.00%
Property Net Revenue and Operating Expense
Total regulated revenue	$ 506,832	$ 536,936	$ 620,259
Total regulated purchased gas costs	205,684	236,337	335,179
Total regulated net revenue	301,148	300,599	285,080
Total regulated operating expenses	170,149	168,944	166,922
Distribution
Property Net Revenue and Operating Expense
Total regulated revenue	380,960	411,978	507,481
Total regulated purchased gas costs	199,381	231,407	334,144
Total regulated net revenue	181,579	180,571	173,337
Total regulated operating expenses	100,205	103,915	100,567
EQT Midstream
Property Net Revenue and Operating Expense
Total regulated revenue	125,872	124,958	112,778
Total regulated purchased gas costs	6,303	4,930	1,035
Total regulated net revenue	119,569	120,028	111,743
Total regulated operating expenses	$ 69,944	$ 65,029	$ 66,355
Gathering and transmission systems
Property, Plant and Equipment:
Minimum estimated service life (in years)	25
Maximum estimated service life (in years)	60
Building
Property, Plant and Equipment:
Estimated service life (in years)	35
Office equipment
Property, Plant and Equipment:
Minimum estimated service life (in years)	3
Maximum estimated service life (in years)	7
Vehicles
Property, Plant and Equipment:
Estimated service life (in years)	5
Computer and telecommunications equipment and systems
Property, Plant and Equipment:
Minimum estimated service life (in years)	3
Maximum estimated service life (in years)	7