Investment in Nonconsolidated Entity (Details) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2018 USD ($)	Mar. 31, 2018 USD ($) Bcf / d mi	Mar. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Percent interest to require approval		66.67%
Issuance of performance guarantee		$ 91.0
Mountain Valley Pipeline
Schedule of Equity Method Investments [Line Items]
Natural gas interstate pipeline (in miles) | mi		300
MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Firms capacity commitments per day (in bcf per day) | Bcf / d		2.0
Duration of firm capacity commitments (in years)		20 years
EQM
Schedule of Equity Method Investments [Line Items]
Total investments		$ 8.8	$ 4.3
EQT Corporation and Subsidiaries | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Firms capacity commitments per day (in bcf per day) | Bcf / d		1.29
MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Capital call notice	$ 65.8
Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Maximum financial statement exposure		$ 637.0
Variable Interest Entity, Not Primary Beneficiary | EQM | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage		45.50%