Revolving Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Line of Credit Facility
Loans outstanding	$ 0		$ 0		$ 0
Letter of credit outstanding amount at the end of period	0		0		0
Maximum amount of outstanding short-term loans at any time during the period	0	178.5	0	178.5
Average daily balance of short-term loans outstanding during the period		26.7		13.4
Weighted average interest rates of average daily balance of short-term loans (as a percent)		0.83%		0.41%
Commitment fee paid to maintain credit facility (as a percent)	0.06%	0.06%	0.12%	0.11%
EQT Midstream Partners
Line of Credit Facility
Loans outstanding	330		330		0
Letter of credit outstanding amount at the end of period	0		0		0
Maximum amount of outstanding short-term loans at any time during the period	450.0	0	450.0	0
Average daily balance of short-term loans outstanding during the period	$ 252.2		$ 173.0
Weighted average interest rates of average daily balance of short-term loans (as a percent)	1.66%		1.68%
Commitment fee paid to maintain credit facility (as a percent)	0.06%	0.06%	0.13%	0.13%