Share-Based Compensation Plans - Narrative (Details) - USD ($)	1 Months Ended	2 Months Ended	12 Months Ended
	Apr. 30, 2022	Feb. 16, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from exercises of all share-based payment arrangements for employees and directors			$ 15,900,000	$ 0	$ 0
Income tax benefit by the exercise of nonqualified employee stock options and vesting of restricted share awards			4,100,000	1,300,000	1,000,000
Cash paid for taxes related to net settlement of share-based incentive awards			24,800,000	3,800,000	600,000
Capitalized compensation cost			5,406,000	4,994,000	3,142,000
Incentive PSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capitalized compensation cost			$ 600,000	$ 800,000	$ 900,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award requisite service period			36 months
Performance Shares | 2021 Incentive PSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs on non-vested awards			$ 7,400,000
Performance Shares | 2022 Incentive PSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs on non-vested awards			$ 29,800,000
Performance Shares | Incentive PSU Programs – Equity Settled
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares, granted (in shares)			575,120	922,260	1,376,198
Grant date fair value (in dollars per share)	$ 75.32		$ 29.73	$ 23.44	$ 6.62
Value of stock awards vested			$ 18,422,830	$ 12,888,876	$ 8,837,327
Shares vested (in shares)			625,563	168,416	73,278
Awards outstanding (in shares)			2,861,990	2,754,648	1,939,728	615,293
Performance Shares | Incentive PSU Programs – Equity Settled | Equitrans Midstream Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)				9,550	7,020
Performance Shares | Incentive PSU Programs – Cash Settled
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of stock awards vested			$ 9,245,564	$ 10,293,571	$ 18,509,929
Shares vested (in shares)			315,333	134,525	153,482
Awards outstanding (in shares)			0	233,580	339,695	452,410
Performance Shares | Incentive PSU Programs – Cash Settled | Equitrans Midstream Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares settled during the period (in shares)				84,697	40,018
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation plan, award as a percentage of target award level			0.00%	0.00%	0.00%	0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation plan, award as a percentage of target award level			220.00%	200.00%	150.00%	300.00%
Performance Share, Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate term			3 years
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capitalized compensation cost			$ 6,600,000	$ 6,700,000	$ 3,000,000
Unrecognized compensation costs on non-vested awards			$ 15,700,000
Non-vested shares, granted (in shares)			1,288,430	1,980,230
Grant date fair value (in dollars per share)			$ 21.65	$ 13.92
Value of stock awards vested			$ 16,644,859	$ 8,612,563	$ 3,200,000
Period for recognition			8 months 12 days
Shares vested (in shares)			1,368,577	621,930
Awards outstanding (in shares)			2,926,945	3,104,281	1,868,400
Restricted stock awards | Equitrans Midstream Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)				59,340
Restricted stock awards | Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares, granted (in shares)			1,288,430	1,980,230	1,767,960
Period after which the shares granted will be fully vested			3 years
Grant date fair value (in dollars per share)			$ 21.65	$ 13.92	$ 10.02
Restricted stock unit awards- liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares, granted (in shares)			0	0	0
Period after which the shares granted will be fully vested			3 years
Deferred compensation liability				$ 8,100,000	$ 4,500,000
Non-qualified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs on non-vested awards			$ 100,000
Number of options granted (in shares)			0	0	1,000,000
Total Intrinsic Value of Exercises			$ 20,200,000
Exercised (in shares)			1,517,407	0	0
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs on non-vested awards			$ 200,000
Grant date fair value (in dollars per share)					$ 10.00
Number of options granted (in shares)			1,240,000
Total Intrinsic Value of Exercises			$ 0
Non-employee directors' share-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)			373,857
Shares granted (in shares)			44,800	120,080	201,300
Weighted average fair value, granted (in dollars per share)			$ 43.97	$ 17.49	$ 13.46
PSU | 2023 Incentive Performance Share Unit Program | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted (in shares)		360,400
PSU | Minimum | 2023 Incentive Performance Share Unit Program | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation plan, award as a percentage of target award level		0.00%
PSU | Maximum | 2023 Incentive Performance Share Unit Program | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation plan, award as a percentage of target award level		200.00%
Restricted Stock Units (RSUs) | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares, granted (in shares)		916,680
Period after which the shares granted will be fully vested		3 years