Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Contract with customer, asset, net	$ 438,600
Revenues from contracts with customers	1,350,198
Gain on derivatives not designated as hedges	62,592	$ 140,742
Other sources of revenue	83,385
Total	$ 1,433,583
Gathering, Transmission, and Storage Services
Disaggregation of Revenue [Line Items]
Number of days in which payment is required	21 days
Natural Gas Sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 1,089,760
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	1,089,760
NGLs Sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	125,468
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	125,468
Oil Sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	11,146
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	$ 11,146
Natural Gas, Oil, and NGLs Sales
Disaggregation of Revenue [Line Items]
Number of days in which payment is required	25 days
Revenues from contracts with customers	$ 1,226,374
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	$ 1,226,374
Water Services
Disaggregation of Revenue [Line Items]
Number of days in which payment is required	21 days
Pipeline, Water and Net Marketing Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 123,824
Other sources of revenue, excluding gain (loss) on derivatives	20,793
Total, excluding gain (loss) on derivatives	144,617
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(232,325)
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	(232,325)
Gain on derivatives not designated as hedges	0	$ 0
EQT Production | Pipeline and Net Marketing Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	38,843
Other sources of revenue, excluding gain (loss) on derivatives	20,793
Total, excluding gain (loss) on derivatives	59,636
EQM Gathering | Firm Reservation Fee Revenue
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	109,933
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	109,933
EQM Gathering | Usage Fees Under Firm Contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12,108
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	12,108
EQM Gathering | Usage Fees Under Interruptible Contract
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,867
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	3,867
EQM Transmission | Firm Reservation Fee Revenue
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	97,775
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	97,775
EQM Transmission | Usage Fees Under Firm Contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,822
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	3,822
EQM Transmission | Usage Fees Under Interruptible Contract
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,337
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	5,337
RMP Gathering | Gathering Revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	52,730
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	52,730
RMP Gathering | Compression Revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,771
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	8,771
RMP Water | Water Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	22,963
Other sources of revenue, excluding gain (loss) on derivatives	0
Total, excluding gain (loss) on derivatives	$ 22,963
Minimum
Disaggregation of Revenue [Line Items]
Contract term			8 years
Maximum
Disaggregation of Revenue [Line Items]
Contract term			15 years