Revolving Credit Facilities (Details)		1 Months Ended	2 Months Ended	12 Months Ended
	Nov. 13, 2017 USD ($) financial_institution	Jul. 31, 2017 USD ($) extension financial_institution	Dec. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2017 USD ($)
Revolving Credit Facility
Line of Credit Facility
Unsecured revolving credit facility	$ 2,500,000,000.0
Long-term line of credit						$ 0
Letters of credit outstanding					$ 0	$ 0
EQT $2.5 Billion Facility | Revolving Credit Facility
Line of Credit Facility
Unsecured revolving credit facility	$ 2,500,000,000.0						$ 1,500,000,000.0
Number of times the maturity date of the credit facility can be extended by one year | extension		2
Number of financial institutions underwriting credit facility of the entity | financial_institution	19
Long-term line of credit			$ 1,300,000,000	$ 1,300,000,000	$ 0
Letters of credit outstanding			159,400,000	$ 159,400,000
Commitment fee paid to maintain credit facility				0.20%	0.23%	0.23%
Maximum amount of outstanding borrowings				$ 1,400,000,000
Average daily balance of loans outstanding				$ 190,900,000
Weighted average interest rates				2.80%
Debt-to-total capitalization ratio (no greater than)				65.00%
EQT $2.5 Billion Facility | Revolving Credit Facility | Maximum
Line of Credit Facility
Unsecured revolving credit facility	$ 3,000,000,000.0
EQM $1.0 Billion Facility
Line of Credit Facility
Commitment fee paid to maintain credit facility				0.20%	0.23%	0.23%
EQM $1.0 Billion Facility | Revolving Credit Facility
Line of Credit Facility
Unsecured revolving credit facility		$ 1,000,000,000					$ 750,000,000
Number of financial institutions underwriting credit facility of the entity | financial_institution		19
Long-term line of credit			180,000,000	$ 180,000,000	$ 0
Letters of credit outstanding			0	0	0
Maximum amount of outstanding borrowings				260,000,000	401,000,000	$ 404,000,000
Average daily balance of loans outstanding				$ 74,000,000	$ 77,000,000	$ 261,000,000
Weighted average interest rates				2.80%	2.00%	1.70%
Additional borrowing capacity		$ 500,000,000
Leverage ratio (not more than)		5.00
Leverage ratio for certain measurement periods (not more than)		5.50
RMP $850 Million Facility | Revolving Credit Facility
Line of Credit Facility
Unsecured revolving credit facility			850,000,000.0	$ 850,000,000.0
Number of financial institutions underwriting credit facility of the entity | financial_institution	18
Long-term line of credit			286,000,000	286,000,000
Letters of credit outstanding			1,000,000.0	1,000,000.0
Average daily balance of loans outstanding			$ 268,000,000
Weighted average interest rates			3.10%
Additional borrowing capacity				$ 200,000,000.0
Leverage ratio (not more than)			4.75	4.75
Leverage ratio for certain measurement periods (not more than)			5.25	5.25
Interest coverage ratio			2.50	2.50
Consolidated leverage ratio			3.50	3.50
RMP $850 Million Facility | Revolving Credit Facility | Minimum
Line of Credit Facility
Commitment fee paid to maintain credit facility			0.375%
RMP $850 Million Facility | Revolving Credit Facility | Maximum
Line of Credit Facility
Commitment fee paid to maintain credit facility			0.50%