Share-Based Compensation Plans - Summary of Restricted Stock Activity (Details) - Restricted Stock - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Non- Vested Shares
Non-vested shares, outstanding, beginning balance (in shares)	192,782
Number of shares granted (in shares)	613,440
Non-vested shares, vested (in shares)	(487,509)
Non-vested shares, forfeited (in shares)	(7,716)
Non-vested shares, outstanding, ending balance (in shares)	310,997	192,782
Weighted Average Fair Value
Weighted average fair value, outstanding, beginning balance (in dollars per share)	$ 59.79
Weighted average fair value, granted (in dollars per share)	17.42
Weighted Average Fair Value, Vested (in dollars per share)	24.33
Weighted Average Fair Value, Forfeited (in dollars per share)	35.16
Weighted average fair value, outstanding, ending balance (in dollars per share)	$ 32.40	$ 59.79
Aggregate Fair Value
Aggregate fair value, outstanding, beginning balance	$ 11,525,593
Aggregate fair value, granted	10,685,274
Aggregate fair value, vested	(11,862,608)	$ (39,800,000)	$ (123,000,000.0)
Aggregate fair value, forfeited	(271,295)
Aggregate fair value, outstanding, ending balance	$ 10,076,964	$ 11,525,593
Equitrans Midstream Employees
Non- Vested Shares
Non-vested shares, outstanding, ending balance (in shares)	71,313