Revolving Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Feb. 18, 2014	Feb. 17, 2014	Dec. 31, 2013
Line of Credit Facility
Revolving credit facility maximum borrowing capacity			$ 1,500
Letter of credit outstanding amount at the end of period	0				0
Loans outstanding	0				0
Maximum amount of outstanding short-term loans at any time during the period	0	0
Commitment fee paid to maintain credit facility (as a percent)	0.06%	0.05%
EQT Midstream Partners
Line of Credit Facility
Revolving credit facility maximum borrowing capacity			750	350
Letter of credit outstanding amount at the end of period	0				0
Loans outstanding	110				0
Maximum amount of outstanding short-term loans at any time during the period	110.0	0
Average daily balance of short-term loans outstanding during the period	$ 92.9
Weighted average interest rates of average daily balance of short-term loans (as a percent)	1.72%
Commitment fee paid to maintain credit facility (as a percent)	0.06%	0.06%