Midstream (EQTNP) 10-K 14 Feb 19 2018 Q4 Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document and Entity Information
Entity Registrant Name	Equitrans Midstream Corporation
Entity Central Index Key	1,747,009
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End	--12-31
Entity Filer Catagorey	Non-accelerated Filer
Entity Emerging Growth Company	false
Small Business Entity	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 0
Entity Common Units, Unit Outstanding		254,271
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q4

Statements of Consolidated Comp

Statements of Consolidated Comprehensive Income - USD ($) shares in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Operating revenues	[1]	$ 1,495,098,000	$ 895,558,000	$ 732,272,000
Operating expenses:
Operating and maintenance	[2]	163,192,000	84,831,000	69,255,000
Selling, general and administrative	[2]	124,069,000	80,339,000	75,512,000
Separation and other transaction costs	[2]	85,444,000	85,124,000	0
Depreciation		175,821,000	96,674,000	62,691,000
Amortization of intangible assets		41,547,000	5,540,000	0
Impairment of long-lived assets		0	0	59,748,000
Impairment of goodwill		261,941,000	0	0
Total operating expenses		852,014,000	352,508,000	267,206,000
Operating income		643,084,000	543,050,000	465,066,000
Equity income	[3]	61,778,000	22,171,000	9,898,000
Other income		5,011,000	4,439,000	27,113,000
Net interest expense	[4]	115,454,000	34,801,000	16,761,000
Income before income taxes		594,419,000	534,859,000	485,316,000
Income tax expense		83,142,000	212,402,000	98,243,000
Net income		511,277,000	322,457,000	387,073,000
Less: Net income attributable to noncontrolling interests		292,879,000	349,613,000	321,920,000
Net income (loss) attributable to Equitrans Midstream Corporation		$ 218,398,000	$ (27,156,000)	$ 65,153,000
Basic:
Weighted average common stock outstanding (in shares)		254,432	254,432	254,432
Net income (loss) (in dollars per share)		$ 0.86	$ (0.11)	$ 0.26
Diluted:
Weighted average common stock outstanding (in shares)		255,033	254,432	255,033
Net income (loss) (in dollars per share)		$ 0.86	$ (0.11)	$ 0.26
Net income		$ 511,277,000	$ 322,457,000	$ 387,073,000
Other comprehensive loss, net of tax:
Pension and other post-retirement benefits liability adjustment, net of tax expense of $638		(1,509,000)	0	0
Other comprehensive loss		(1,509,000)	0	0
Comprehensive income		509,768,000	322,457,000	387,073,000
Less: Comprehensive income attributable to noncontrolling interests		292,879,000	349,613,000	321,920,000
Comprehensive income (loss) attributable to Equitrans Midstream Corporation		$ 216,889,000	$ (27,156,000)	$ 65,153,000
[1]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of approximately $1.1 billion, $665.9 million and $551.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 8.
[2]	perating and maintenance expense included charges from EQT of $49.8 million, $40.6 million and $34.2 million for the years ended December 31, 2018, 2017 and 2016, respectively. Selling, general and administrative expense included charges from EQT of $85.1 million, $75.6 million and $70.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 8. Separation and other transaction costs represent selling, general and administrative expenses related to the Rice Merger, the EQM-RMP Mergers, the Drop-Down Transaction, the Separation and the EQGP Buyout (each defined in Note 1) and included charges from EQT of $53.3 million and $85.1 million for the years ended December 31, 2018 and 2017, respectively. See Notes 1 and 8.
[3]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 7.
[4]	Net interest expense included interest income on the Preferred Interest (defined in Note 1) of $6.6 million, $6.8 million and $1.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. Other income included distributions received from EES (defined in Note 1) of $8.3 million for the year ended December 31, 2016. See Note 1.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension and other post-retirement benefits liability adjustment, tax expense		$ 638
Operating revenues		1,111,289	$ 665,939	$ 551,353
Operating and maintenance expense	[1]	163,192	84,831	69,255
Selling, general and administrative expense	[1]	124,069	80,339	75,512
Transaction costs	[1]	85,444	85,124	0
Interest income from the Preferred Interest		6,578	6,818	1,740
EQT Corporation
Operating revenues		1,100,000	665,900	551,400
Operating and maintenance expense		49,800	40,600	34,200
Selling, general and administrative expense		85,100	75,600	70,400
Transaction costs		53,300	85,100
EES
Interest income from the Preferred Interest		$ 6,600	$ 6,800	1,700
Distributions included in other income				$ 8,300
[1]	perating and maintenance expense included charges from EQT of $49.8 million, $40.6 million and $34.2 million for the years ended December 31, 2018, 2017 and 2016, respectively. Selling, general and administrative expense included charges from EQT of $85.1 million, $75.6 million and $70.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 8. Separation and other transaction costs represent selling, general and administrative expenses related to the Rice Merger, the EQM-RMP Mergers, the Drop-Down Transaction, the Separation and the EQGP Buyout (each defined in Note 1) and included charges from EQT of $53.3 million and $85.1 million for the years ended December 31, 2018 and 2017, respectively. See Notes 1 and 8.

Statements of Consolidated Cash

Statements of Consolidated Cash Flows - USD ($)		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Cash flows from operating activities:
Net income		$ 511,277,000		$ 322,457,000		$ 387,073,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation		175,821,000		96,674,000		62,691,000
Amortization of intangible assets		41,547,000		5,540,000		0
Impairment of long-lived assets		0		0		59,748,000
Impairment of goodwill		261,941,000		0		0
Deferred income taxes		25,246,000		158,369,000		(17,576,000)
Equity income	[1]	(61,778,000)		(22,171,000)		(9,898,000)
AFUDC — equity		(5,570,000)		(5,110,000)		(19,402,000)
Non-cash long-term compensation expense		4,190,000		468,000		373,000
Changes in other assets and liabilities:
Accounts receivable		(36,225,000)		(24,569,000)		(3,718,000)
Accounts payable		(90,502,000)		130,347,000		87,099,000
Other assets and other liabilities		(104,237,000)		7,736,000		3,115,000
Net cash provided by operating activities		721,710,000		669,741,000		549,505,000
Cash flows from investing activities:
Capital expenditures		(865,882,000)		(380,151,000)		(584,819,000)
Capital contributions to the MVP Joint Venture		(913,195,000)		(159,550,000)		(98,399,000)
(Purchases)/ Sales of interests in the MVP Joint Venture		(11,302,000)		0		12,533,000
Principal payments received on the Preferred Interest		4,406,000		4,166,000		1,024,000
Net cash used in investing activities		(1,785,973,000)		(535,535,000)		(669,661,000)
Cash flows from financing activities:
Proceeds from the issuance of EQM common units, net of offering costs		0		0		217,102,000
Proceeds from credit facility borrowings		3,446,500,000		544,000,000		740,000,000
Payments on credit facility borrowings		(3,271,000,000)		(344,000,000)		(1,039,000,000)
Proceeds from the issuance of long-term debt		600,000,000		0		0
Net (payments on) proceeds from EQGP's working capital loan with EQT		(168,000)		84,000		18,000
Net (distributions to) contributions from EQT		(1,117,577,000)		(1,009,501,000)		203,926,000
Net contribution to Strike Force Midstream LLC by minority owner		0		6,738,000		0
Distributions paid to noncontrolling interest unitholders		(380,651,000)		(236,123,000)		(189,981,000)
Debt discount, debt issuance costs and credit facility origination fees		(73,467,000)		(2,257,000)		(8,580,000)
Net cash provided by (used in) financing activities		1,237,431,000		(1,041,059,000)		423,485,000
Net change in cash and cash equivalents		173,168,000		(906,853,000)		303,329,000
Cash and cash equivalents at beginning of year		121,004,000	[2]	966,270,000		662,941,000	[2]
Cash and cash equivalents at beginning of year	[2]					1,027,857,000
Cash and cash equivalents at end of year		294,172,000		121,004,000	[2]	966,270,000
Strike Force Midstream
Cash flows from financing activities:
Acquisition of 25% of Strike Force Midstream LLC		(175,000,000)		0		0
EQGP
Cash flows from financing activities:
Acquisition of 25% of Strike Force Midstream LLC		(291,206,000)		0		0
EQT Corporation | Affiliated Entity
Cash flows from financing activities:
Net (payments on) proceeds from EQGP's working capital loan with EQT		(168,000)		84,000		18,000
EQM | Affiliated Entity
Cash flows from financing activities:
Net (payments on) proceeds from EQGP's working capital loan with EQT		$ 2,500,000,000		$ 0		$ 500,000,000
[1]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 7.
[2]	Cash and cash equivalents at beginning of year for December 31, 2017 includes $61.6 million of cash and cash equivalents acquired at the effective time of the Rice Merger. See Note 2.

Statements of Consolidated Ca_2

Statements of Consolidated Cash Flows (Parenthetical) $ in Millions	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents acquired	$ 61.6

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents		$ 294,172	$ 121,004	[1]
Accounts receivable (net of allowance for doubtful accounts of $75 and $446 as of December 31, 2018 and 2017, respectively) (a)		255,496	219,271
Other current assets		19,171	14,565
Total current assets		568,839	354,840
Property, plant and equipment		6,469,846	5,516,527
Less: accumulated depreciation		(602,199)	(405,665)
Net property, plant and equipment		5,867,647	5,110,862
Investment in unconsolidated entity		1,510,289	460,546
Goodwill		1,239,269	1,384,872
Net intangible assets		576,113	617,660
Deferred income taxes		597,321	257,128
Other assets		164,357	142,888
Total assets		10,523,835	8,328,796
Current liabilities:
Current portion of long-term debt		6,000	0
Accounts payable	[2]	210,007	468,422
Capital contribution payable to the MVP Joint Venture		169,202	105,734
Accrued interest		80,236	11,067
Accrued liabilities		84,011	20,995
Total current liabilities		549,456	606,218
Credit facility borrowings		641,500	466,000
EQM senior notes		3,456,639	987,352
Long-term debt		562,105	0
Regulatory and other long-term liabilities		54,502	30,462
Total liabilities		5,264,202	2,090,032
Shareholders' equity:
Parent net investment		0	1,143,769
Common stock, no par value, authorized 1,250,000 shares, issued 254,271 shares in 2018		425,370	0
Retained earnings		33,932	0
Accumulated other comprehensive loss		(1,509)	0
Total common shareholders' equity		457,793	1,143,769
Noncontrolling interests		4,801,840	5,094,995
Total shareholders' equity		5,259,633	6,238,764
Total liabilities and shareholders' equity		$ 10,523,835	$ 8,328,796
[1]	Cash and cash equivalents at beginning of year for December 31, 2017 includes $61.6 million of cash and cash equivalents acquired at the effective time of the Rice Merger. See Note 2.
[2]	Accounts receivable as of December 31, 2018 and 2017 included $175.9 million and $158.7 million, respectively of accounts receivable due from EQT, a related party. Accounts payable as of December 31, 2018 and 2017 included $34.1 million and $363.1 million, respectively, of accounts payable due to EQT.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, for doubtful accounts	$ 75	$ 446
Common stock, shares authorized (in shares)	1,250,000,000
Common stock, shares issued (In shares)	254,271,000
Accounts receivable – related parties	$ 175,869	158,720
Accounts payable - related parties	$ 34,100	$ 363,100

Statements of Consolidated Equi

Statements of Consolidated Equity - USD ($) shares in Thousands, $ in Thousands		Total		Parent Net Investment		Common Stock	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Beginning balance at Dec. 31, 2015		$ 2,051,548		$ (898,703)		$ 0	$ 0	$ 0	$ 2,950,251
Shares Outstanding, beginning balance (in shares) at Dec. 31, 2015						0
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		387,073		65,153					321,920
Net (contributions)/distributions to EQT		740,797		740,797
Share-based compensation plans		373		212					161
Distributions paid to noncontrolling interest unitholders		(189,981)							(189,981)
Issuance of Equitrans Midstream common stock		217,102							217,102
Pension and other post-retirement benefits liability adjustment, net of tax expense of $638		0
Net changes in ownership of consolidated entities		(16,191)		24,296					(40,487)
Elimination of net current and deferred tax liabilities		1,945		1,945
Shares Outstanding, ending balance (in shares) at Dec. 31, 2016						0
Ending balance at Dec. 31, 2016		3,192,666		(66,300)		$ 0	0	0	3,258,966
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		322,457		(27,156)					349,613
Net (contributions)/distributions to EQT		(893,682)		(893,682)
Net contribution to Strike Force Midstream LLC by minority owner		6,738							6,738
Share-based compensation plans		468		278					190
Distributions paid to noncontrolling interest unitholders		(236,123)							(236,123)
Pension and other post-retirement benefits liability adjustment, net of tax expense of $638		0
Rice Merger	[2]	3,846,240	[1]	2,130,629	[1]				1,715,611
Shares Outstanding, ending balance (in shares) at Dec. 31, 2017						0
Ending balance at Dec. 31, 2017		6,238,764		1,143,769		$ 0	0	0	5,094,995
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		511,277		184,466			33,932		292,879
Net (contributions)/distributions to EQT		(701,901)		(701,901)
Share-based compensation plans (in shares)						2
Share-based compensation plans		4,190		340		$ 2,897			953
Distributions paid to noncontrolling interest unitholders		(380,651)							(380,651)
Issuance of Equitrans Midstream common stock (in shares)						254,269
Issuance of Equitrans Midstream common stock		0
Pension and other post-retirement benefits liability adjustment, net of tax expense of $638		(1,509)						(1,509)
Net changes in ownership of consolidated entities		55,669		(159,255)					214,924
Purchase of Strike Force Midstream LLC noncontrolling interests		(175,000)		1,818					(176,818)
Separation-related adjustments		0		(469,237)		$ 469,237
Purchase of EQGP common units		(291,206)				$ (46,764)			(244,442)
Shares Outstanding, ending balance (in shares) at Dec. 31, 2018						254,271
Ending balance at Dec. 31, 2018		$ 5,259,633		$ 0		$ 425,370	$ 33,932	$ (1,509)	$ 4,801,840
[1]	Net interest expense included interest income on the Preferred Interest (defined in Note 1) of $6.6 million, $6.8 million and $1.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. Other income included distributions received from EES (defined in Note 1) of $8.3 million for the year ended December 31, 2016. See Note 1.
[2]	Represents the estimated fair value of the Rice Midstream Holdings LLC net assets acquired by EQT and allocated to Equitrans Midstream Corporation as part of the Rice Merger. See Notes 1 and 2.

Statements of Consolidated Eq_2

Statements of Consolidated Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension and other post-retirement benefits liability adjustment, tax expense	$ 638
Common stock, shares authorized (in shares)	1,250,000,000
Preferred shares, authorized (in shares)	50,000,000
Preferred shares, issued (in shares)	0
Preferred shares, outstanding (in shares)	0
EQM Midstream Partners, LP
Cash distributions declared per unit (in dollars per share)	$ 4.295	$ 3.655	$ 3.05
EQGP
Cash distributions declared per unit (in dollars per share)	1.123	$ 0.806	$ 0.571
RMP
Cash distributions declared per unit (in dollars per share)	$ 0.5966

Summary of Operations and Signi

Summary of Operations and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Operations and Significant Accounting Policies	Summary of Operations and Significant Accounting Policies Organization On February 21, 2018, EQT announced its plan to separate its midstream business, which was composed of the separately-operated natural gas gathering, transmission and storage and water services of EQT (collectively, the Midstream Business), from its upstream business, which was composed of the natural gas, oil and natural gas liquids development, production and sales and commercial operations of EQT (collectively, the Upstream Business) (the Separation). Equitrans Midstream Corporation (together with its subsidiaries, Equitrans Midstream or the Company) was incorporated on May 11, 2018 as a wholly-owned subsidiary of EQT to hold the assets, liabilities and results of operations of EQT's Midstream Business. On November 12, 2018, Equitrans Midstream, EQT and, for certain limited purposes, EQT Production Company, a wholly-owned subsidiary of EQT, entered into a separation and distribution agreement (the Separation and Distribution Agreement), pursuant to which, among other things, EQT effected the Separation, including the transfer of certain assets and liabilities to the Company, and distributed 80.1% of the then outstanding shares of common stock, no par value, of Equitrans Midstream (Equitrans Midstream common stock) to EQT shareholders of record as of the close of business on November 1, 2018 (the Distribution). The Distribution was effective at 11:59 p.m., Eastern Time, on November 12, 2018 (the Separation Date). EQT retained the remaining 19.9% of the outstanding shares in Equitrans Midstream (the Retained Interest). Post-Separation, the Company holds investments in the entities then-conducting the Midstream Business, including limited and general partner interests in EQGP Holdings, LP (formerly known as EQT GP Holdings, LP) (EQGP), which, as of December 31, 2018, owned limited partner interests, the entire general partner interest and all of the incentive distribution rights (IDRs) in EQM Midstream Partners, LP (formerly known as EQT Midstream Partners, LP) (NYSE: EQM) (EQM). As of December 31, 2018, EQGP was a subsidiary of Equitrans Gathering Holdings, LLC (formerly known as EQT Gathering Holdings, LLC) (Equitrans Gathering Holdings). Following the closing of the EQGP Unit Purchases and the exercise of the Limited Call Right (each defined and discussed in Note 6 and collectively referred to as the EQGP Buyout), EQGP became an indirect, wholly-owned subsidiary of the Company. EQM owns, operates, acquires and develops midstream assets in the Appalachian Basin. As of December 31, 2018, EQM Midstream Services, LLC (formerly known as EQT Midstream Services, LLC) (the EQM General Partner) was a wholly-owned subsidiary of EQGP and EQM's general partner. As of December 31, 2018, EQGP Services, LLC (formerly known as EQT GP Services, LLC) (the EQGP General Partner) was a wholly-owned subsidiary of Equitrans Gathering Holdings and EQGP's general partner. The Company's assets, liabilities and results of operations also include the legacy assets of Rice Midstream Holdings LLC (Rice Midstream Holdings). EQT obtained control of Rice Midstream Holdings on November 13, 2017 (the Rice Merger Date), when, pursuant to the agreement and plan of merger dated June 19, 2017 by and among EQT, Rice Energy Inc. (Rice Energy) and a wholly-owned subsidiary of EQT (EQT Merger Sub), Rice Energy became a wholly-owned, indirect subsidiary of EQT, and EQT became the indirect parent of Rice Midstream Holdings (the Rice Merger). The operations of Rice Midstream Holdings were primarily conducted through RM Partners LP (formerly known as Rice Midstream Partners LP) (RMP), Rice West Virginia Midstream LLC (now known as EQM West Virginia Midstream LLC) (EQM West Virginia), Rice Olympus Midstream LLC (now known as EQM Olympus Midstream LLC) (EQM Olympus) and Strike Force Midstream Holdings LLC (Strike Force Holdings). At the Rice Merger Date, Strike Force Holdings owned 75% of the outstanding limited liability company interests in Strike Force Midstream LLC (Strike Force Midstream), a Delaware limited liability company. Rice Midstream Holdings, through its wholly-owned, indirect subsidiary Rice Midstream GP Holdings LP (RMGP), owned Rice Midstream Management LLC (now known as EQM Midstream Management LLC), RMP's general partner (the RMP General Partner), as well as limited partner interests and all of the IDRs in RMP. Rice Midstream Holdings controlled the RMP General Partner and therefore consolidated the results of RMP. In 2018, EQM obtained control of the operating entities of Rice Midstream Holdings through the following transactions: • On April 25, 2018, EQM, RMP and certain of their affiliates entered into an agreement and plan of merger, pursuant to which EQM acquired RMP and the RMP General Partner (the EQM-RMP Mergers). The EQM-RMP Mergers closed on July 23, 2018. • On May 1, 2018, EQM acquired 25% of the outstanding limited liability company interests in Strike Force Midstream from Gulfport Midstream Holdings, LLC (Gulfport Midstream), an affiliate of Gulfport Energy Corporation, in exchange for $175 million in cash (the Gulfport Transaction). • On May 22, 2018, and effective May 1, 2018, EQM, through its wholly-owned subsidiary EQM Gathering Holdings, LLC, a Delaware limited liability company (EQM Gathering), acquired all the outstanding limited liability company interests in each of EQM West Virginia, EQM Olympus and Strike Force Holdings (collectively the Drop-Down Entities), pursuant to the terms of a contribution and sale agreement dated as of April 25, 2018 by and among EQM, EQM Gathering, EQT and Rice Midstream Holdings, in exchange for an aggregate of 5,889,282 common units representing limited partner interests in EQM (EQM common units) and cash consideration of $1.15 billion , plus working capital adjustments (the Drop-Down Transaction). As a result of the closing of the Drop-Down Transaction, effective May 1, 2018, the Drop-Down Entities and Strike Force Midstream became indirect, wholly-owned subsidiaries of EQM. Basis of Presentation As of December 31, 2018, the EQGP General Partner was a wholly-owned subsidiary of Equitrans Gathering Holdings and controlled EQGP through its general partner interest in EQGP; therefore, the financial statements of the Company consolidate EQGP. As of December 31, 2018, the EQM General Partner was a wholly-owned subsidiary of EQGP and controlled EQM through its general partner interest in EQM; therefore, the financial statements of EQGP consolidated EQM. For each of the periods prior to the Separation presented in this Annual Report on Form 10-K, the consolidated financial statements and related notes include the assets, liabilities and results of operations of the Midstream Business that were transferred to the Company upon the closing of the Distribution and represent the predecessor for accounting purposes of Equitrans Midstream (the Predecessor). Predecessor financial information has been derived from EQT's consolidated financial statements and accounting records and reflects the historical results of operations, financial position and cash flows of the Company as if the Midstream Business had been consolidated for all periods presented. The financial statements include expense allocations for certain corporate functions historically performed by EQT, such as executive oversight, accounting, treasury, tax, legal, procurement, information technology and share-based compensation. See Note 8 . The Company believes the assumptions underlying the consolidated financial statements are reasonable; however, as organizational structure and strategic focus dictate expenses incurred, the financial statements may not include all expenses that would have been incurred had the Company existed as a standalone, publicly traded company for the entirety of the three years ended December 31, 2018. Similarly, the financial statements may not reflect the results of operations, financial position and cash flows had the Company existed as a standalone, publicly traded company. References in these financial statements to Equitrans Midstream or the Company refer collectively to Equitrans Midstream Corporation and the Predecessor as applicable for all periods presented. Nature of Business The Company, through its control of EQM, provides midstream services to its customers in Pennsylvania, West Virginia and Ohio through its three primary assets: the gathering system, which delivers natural gas from wells and other receipt points to transmission pipelines; the transmission and storage system, which delivers natural gas to local demand users and interstate pipelines for access to demand markets; and the water service system, which consists of water pipelines, impoundment facilities, pumping stations, take point facilities and measurement facilities that support well completion activities and collect flowback and produced water for recycling or disposal. As of December 31, 2018 , the gathering system included approximately 700 miles of high-pressure gathering lines with total contracted firm reservation capacity of approximately 2.4 billion cubic feet (Bcf) per day, compression of approximately 333,000 horsepower and multiple interconnect points with the Company's transmission and storage system and to other interstate pipelines. The gathering system also included approximately 1,500 miles of Federal Energy Regulatory Commission (FERC)-regulated, low-pressure gathering lines. As of December 31, 2018 , the transmission and storage system included approximately 950 miles of FERC-regulated, interstate pipeline that have interconnect points to seven interstate pipelines and local distribution companies (LDCs). The transmission and storage system is supported by 41 compressor units, with total throughput capacity of approximately 4.4 Bcf per day and compression of approximately 120,000 horsepower, and 18 associated natural gas storage reservoirs, which have a peak withdrawal capacity of approximately 645 million cubic feet (MMcf) per day and a working gas capacity of approximately 43 Bcf. As of December 31, 2018 , the water system included two independent systems composed of approximately 160 miles of pipeline that deliver fresh water from the Monongahela River, the Ohio River, local reservoirs and several regional waterways. The fresh water delivery services systems consist of permanent, buried pipelines, surface pipelines and fresh water storage facilities, as well as pumping stations and 28 fresh water impoundment facilities, which support fresh water transportation throughout the systems, and take point facilities and measurement facilities, which support well completion activities and collect and recycle or dispose flowback and produced water. Significant Accounting Policies Principles of Consolidation. The Company, for the periods presented in these consolidated financial statements prior to November 12, 2018, did not exist as a standalone, publicly-traded company holding the Midstream Business. Therefore, these consolidated financial statements are reflective of the Predecessor as applicable as described in "Basis of Presentation." Investments over which the Company can exert significant influence, but not control, are recorded under the equity method of accounting. Intercompany transactions have been eliminated for purposes of preparing these consolidated financial statements. Transactions between EQT, on the one hand, and the Company, EQGP or EQM, on the other hand, during the period prior to the Separation Date, have been identified and presented as transactions between related parties as discussed in Note 8 . Segments. Operating segments are revenue-producing components of the enterprise for which separate financial information is produced internally and is subject to evaluation by the Company's chief operating decision maker in deciding how to allocate resources. The Company reports its operations in three segments that reflect its three lines of business of Gathering, Transmission and Water. The operating segments are evaluated based on their contribution to the Company's operating income and equity income. Transmission also includes the Company's investment in the MVP Joint Venture, which is treated as an equity investment for accounting purposes as described in Note 7 ; as a result, Transmission's portion of the MVP Joint Venture's operating results is reflected in equity income and not in Transmission's operating income. All of the Company's operating revenues, income and assets are generated or located in the United States. See Note 5 for financial information by segment. Reclassification. Certain previously reported amounts have been reclassified to conform to the current year presentation. Use of Estimates. The preparation of financial statements in conformity with U.S. Generally Accepted Accounting Principles (GAAP) requires management to make estimates and assumptions that affect amounts reported in these financial statements. Actual results could differ from those estimates. The Company's Post-Separation Relationship with EQT. Following the Separation and Distribution, the Company and EQT are separate companies with separate management teams and separate boards of directors, however, due to the Retained Interest held by EQT as of December 31, 2018, the Company and EQT remain related parties. See Note 8. In connection with the Distribution, the Company and EQT executed the Separation and Distribution Agreement and various other agreements, including the Transition Services Agreement, the Tax Matters Agreement, the Employee Matters Agreement and the Shareholder and Registration Rights Agreement (each defined and discussed in Note 8), to effect the Separation and provide a framework for their relationship after the Separation. These agreements provide for, among other things, the identification and transfer of the Midstream Business' assets, employees, liabilities and obligations (including investments, property, plant and equipment, employee benefits and tax-related assets and liabilities) to the Company and govern the relationship between the Company and EQT subsequent to the Separation. Net transfers and settlements related to the Separation and Distribution were presented as a net distribution to EQT on the statement of consolidated equity for the year ended December 31, 2018. Cash Equivalents. The Company classifies highly-liquid investments with original maturities of three months or less as cash equivalents. Interest earned on cash equivalents is recorded as a reduction to net interest expense on the statements of comprehensive income. Accounts Receivables. Trade and other receivables are stated at their historical carrying amount. Judgment is required to assess the ultimate realization of accounts receivable, including assessing the probability of collection and the creditworthiness of customers. Based on assessments by management, allowances for doubtful accounts were $0.1 million and $0.4 million at December 31, 2018 and 2017 , respectively. The Company also has receivables due from EQT as discussed in Note 8 . Fair Value of Financial Instruments. The Company categorizes assets and liabilities disclosed at fair value using a three-level fair value hierarchy based on priority of the inputs used in the valuation. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Owing to their short maturity, the carrying values of cash and cash equivalents, accounts receivable and accounts payable are assumed to approximate fair value; as such, their fair values are Level 1 fair value measurements. Interest rates on credit facility borrowings are based on prevailing market rates, so the carrying values of the credit facility borrowings approximate fair value and the fair values are Level 1 fair value measurements. As the Company's Term Loans (defined in Note 10 ) and EQM's senior notes are not actively traded, their fair values are estimated using an income approach model that applies a discount rate based on prevailing market rates for debt with similar remaining time-to-maturity and credit risk; as such, their fair values are Level 2 fair value measurements. See Note 10 . The fair value of the Preferred Interest is estimated using an income approach model that applies a discount rate based on prevailing market rates and is a Level 3 fair value measurement. As of December 31, 2018 and 2017 , the estimated fair value of the Preferred Interest was approximately $122 million and $133 million , respectively, and the carrying value of the Preferred Interest was approximately $115 million and $119 million , respectively, inclusive of $4.4 million for each period reported in other current assets on the consolidated balance sheets. Property, Plant and Equipment. The Company's property, plant and equipment are stated at depreciated cost. Maintenance projects that do not increase the overall life of the related assets are expensed as incurred. Expenditures that extend the useful life of the asset are capitalized. The Company capitalized internal costs of $54.4 million , $46.5 million and $53.2 million in the years ended December 31, 2018, 2017 and 2016 , respectively. The Company capitalized interest, including the debt component of Allowance for Funds Used During Construction (AFUDC), of $12.6 million , $4.7 million and $9.4 million in the years ended December 31, 2018, 2017 and 2016 , respectively. The following table summarizes the Company's property, plant and equipment. December 31, 2018 2017 (Thousands) Gathering assets $ 4,387,908 $ 3,642,937 Accumulated depreciation (247,720 ) (153,791 ) Net gathering assets 4,140,188 3,489,146 Transmission and storage assets 1,785,157 1,674,080 Accumulated depreciation (286,693 ) (248,474 ) Net transmission and storage assets 1,498,464 1,425,606 Water services assets 194,465 193,825 Accumulated depreciation (26,489 ) (3,363 ) Net water services assets 167,976 190,462 Net other property, plant and equipment 61,019 5,648 Net property, plant and equipment $ 5,867,647 $ 5,110,862 Depreciation is recorded using composite rates on a straight-line basis over the estimated useful life of the asset. The average depreciation rates for the years ended December 31, 2018, 2017 and 2016 were 2.7% , 1.8% and 2.2% , respectively. The Company estimates that gathering and transmission pipelines have useful lives of 20 years to 65 years and compression equipment has useful lives of 20 years to 50 years . The Company estimates that water pipelines, pumping stations and impoundment facilities have useful lives of 10 years to 15 years . As circumstances warrant, depreciation estimates are reviewed to determine if any changes in the underlying assumptions are necessary. Equitrans, L.P., the Company's FERC-regulated subsidiary, re-evaluates depreciation rates for its regulated property, plant and equipment each time it files with the FERC for a change in transmission and storage rates. Intangible Assets. Intangible assets are recorded under the acquisition method of accounting at their estimated fair values at the acquisition date, which are calculated as the present value of estimated future cash flows using a risk-adjusted discount rate. The Company did not have any intangible assets prior to the Rice Merger. At the Rice Merger Date, through pushdown accounting, the Company recorded $623.2 million of intangible assets associated with acquired customer relationships. See Note 2 . The Company's intangible assets have a useful life of 15 years and are amortized on a straight-line basis. Accumulated amortization as of December 31, 2018 and 2017 was $47.0 million and $5.5 million , respectively. Estimated annual amortization for the next five years is $41.5 million . Impairment of Long-lived Assets. Whenever events or changes in circumstances indicate that the carrying value of its long-lived assets may not be recoverable, the Company reviews its long-lived assets for impairment by first comparing the carrying value of the asset to the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the assets. If the carrying value exceeds the sum of the undiscounted cash flows, the Company estimates and recognizes an impairment loss equal to the difference between the carrying value and fair value of the assets. During the fourth quarter of 2018, a triggering event occurred as a result of the Company's annual goodwill impairment evaluation, which required the Company to perform a recoverability test on its long-lived assets. No impairment was recorded as a result of the recoverability test. No impairment of any long-lived assets was indicated or recorded during the year ended December 31, 2017 . During the year ended December 31, 2016, the Company recorded an impairment of long-lived assets of $59.7 million related to certain gathering assets. Using the income approach and Level 3 fair value measurement inputs, the gathering assets were written down to fair value. The impairment was triggered by a reduction in estimated future cash flows caused by the low commodity price environment, which reduced producer drilling activity and related throughput on the gathering assets. Goodwill. Goodwill is the total consideration of an acquisition less the fair value of the identifiable, acquired net assets. As a result of the Rice Merger, Rice Midstream Holdings recorded goodwill to two reporting units within the Gathering segment. See Note 2 . Prior to the Rice Merger, the Company had no goodwill. Goodwill is evaluated for impairment at least annually and whenever events or changes in circumstance indicate that the fair value of a reporting unit is less than its carrying amount. The Company may perform either a qualitative or quantitative assessment of potential impairment. The Company's qualitative assessment of potential impairment may result in the determination that a quantitative impairment analysis is not necessary. Under this elective process, the Company assesses qualitative factors to determine whether the existence of events or circumstances leads the Company to determine that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If after assessing the totality of events or circumstances, the Company determines that it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then performing a quantitative analysis is not required. However, if the Company concludes otherwise, then it performs a quantitative impairment analysis. If the Company chooses not to perform a qualitative assessment, or if it chooses to perform a qualitative assessment but is unable to qualitatively conclude that no impairment has occurred, then the Company will perform a quantitative evaluation. In the case of a quantitative assessment, the Company estimates the fair value of the reporting unit with which the goodwill is associated and compares it to the carrying value. If the estimated fair value of a reporting unit is less than its carrying value, an impairment charge is recognized for the excess of the reporting unit's carrying value over its fair value. The two reporting units to which the Company's goodwill is recorded are (i) Rice Retained Midstream, which comprises the Ohio gathering assets acquired in the Rice Merger, and (ii) RMP PA Gas Gathering, which comprises the Pennsylvania gathering assets acquired the Rice Merger. Rice Retained Midstream and RMP PA Gas Gathering earn a substantial portion of their revenues from volumetric-based fees, which are sensitive to changes in their customers' development plans. Following the third quarter of 2018 and prior to the Separation, the Company identified impairment indicators in the form of production curtailments announced by a primary customer of the Rice Retained Midstream and RMP PA Gas Gathering reporting units that could reduce volumetric-based fee revenues of those reporting units. In estimating the fair value of its reporting units, the Company used a combination of the income approach and the market approach. The Company used the income approach's discounted cash flow method, which applies significant inputs not observable in the public market (Level 3), including estimates and assumptions related to future throughput volumes, operating costs, capital spending and changes in working capital. The Company used the market approach's comparable company method and reference transaction method. The comparable company method evaluates the value of a company using metrics of other businesses of similar size and industry. The reference transaction method evaluates the value of a company based on pricing multiples derived from similar transactions entered into by similar companies. For the year ended December 31, 2018, the Company determined that the carrying value of the RMP PA Gas Gathering reporting unit was greater than its fair value; however, the fair value of the Rice Retained Midstream reporting unit exceeded its carrying value. As a result, the Company recognized impairment of goodwill of $261.9 million , with a corresponding decrease to goodwill on the consolidated balance sheet. Investment in Unconsolidated Entity. The Company reviews the carrying value of its investments in unconsolidated entities for impairment whenever events or changes in circumstances indicate that the carrying value may have declined in value. The impairment review involves comparing the investment's carrying value to its estimated fair value. If the carrying value exceeds the estimated fair value, the Company estimates and recognizes an impairment loss equal to the difference between the investment's carrying value and fair value. Preferred Interest. EQT Energy Supply, LLC, a subsidiary of EQT (EES), generates revenue by providing services to a local distribution company. Upon EQM's acquisition of the preferred interest in EES (the Preferred Interest) in April 2015 and through October 2016, the Preferred Interest was treated as a cost method investment for accounting purposes. In October 2016, the EES operating agreement was amended to provide for mandatory redemption of the Preferred Interest at the end of the preference period, which is expected to be December 31, 2034. As a result of the amendment, EQM's investment in EES converted from a cost method investment to a note receivable effective October 1, 2016. The change did not affect the carrying value of the instrument but did affect the financial statement classification and presentation of distributions from EES. Distributions from EES received prior to the amendment were included in other income in EQM's statements of consolidated operations; distributions received after the amendment are recorded partly as a reduction to the Preferred Interest and partly as interest income, which is included in net interest expense in EQM's statements of consolidated comprehensive income. Unamortized Debt Discount and Issuance Costs. The Company amortizes debt discounts and issuance costs over the term of the related borrowing. Costs incurred from the issuance and extension of the EQM Credit Facility (defined in Note 10 ) and the issuance of the Equitrans Midstream Credit Facility and Equitrans Midstream Term Loan Credit Facility (each as defined in Note 10 ) are presented in other assets on the consolidated balance sheets. Debt discounts and issuance costs for all other debt instruments are presented as a reduction to debt on the consolidated balance sheets. Gas Imbalances. Gas imbalances occur when the actual amount of gas delivered from a pipeline system or storage facility varies from the amount of gas scheduled for delivery. The Company values gas imbalances due to/from shippers and operators at current index prices. Gas imbalances are settled in-kind, subject to the terms of the FERC tariffs. As of December 31, 2018 and 2017 , gas imbalance receivables of $3.3 million and $5.2 million , respectively, were presented in other current assets, with offsetting amounts recorded to system gas, a component of property, plant and equipment, on the consolidated balance sheets. The Company classifies gas imbalances as current because they are expected to settle within one year. Asset Retirement Obligations. The Company has asset retirement obligations related to its water system and to one of its compression stations, for which the Company recorded an associated liability and capitalized a corresponding amount to asset retirement costs. The liability relates to the expected future obligation to dismantle, reclaim and dispose of these assets and was estimated using the present value of expected future cash flows, adjusted for inflation and discounted at the Company's credit-adjusted, risk-free rate. Asset retirement obligations are recorded in regulatory and other long-term liabilities on the consolidated balance sheets. The following table presents a reconciliation of the beginning and ending carrying amounts of the Company's asset retirement obligations. December 31, 2018 2017 (Thousands) Asset retirement obligation at beginning of period $ 9,321 $ — Liabilities assumed at Rice Merger — 9,286 Liabilities incurred 231 — Revisions to estimated liabilities (a) 1,928 — Accretion expense 455 35 Asset retirement obligation at end of period $ 11,935 $ 9,321 (a) Revisions to estimated liabilities reflect changes in retirement cost assumptions and to the estimated timing of liability settlement. The Company is not legally or contractually obligated to restore or dismantle its transmission and storage system. The Company is legally required to operate and maintain these assets and intends to do so as long as supply and demand for natural gas exists, which the Company expects to continue into the foreseeable future. Therefore, the Company did not have any asset retirement obligations related to its transmission and storage assets as of December 31, 2018 and 2017 . Contingencies. EQM is involved in various regulatory and legal proceedings that arise in the ordinary course of business. A liability is recorded when the loss is probable and the amount of loss can be reasonably estimated. EQM considers many factors when making such assessments, including historical knowledge and matter specifics. Estimates are developed through consultation with legal counsel and analysis of the potential results. See Note 13 . Regulatory Accounting. Equitrans, L.P. owns all of the Company's gathering, transmission and storage operations as well as its low-pressure gathering assets. Equitrans, L.P. is subject to FERC regulation. Through the rate-setting process, rate regulation allows Equitrans, L.P. to recover the costs of providing regulated services plus an allowed return on invested capital. Regulatory accounting allows Equitrans, L.P. to defer expenses and income to its consolidated balance sheets as regulatory assets and liabilities when it is probable that those expenses and income will be allowed in the rate-setting process for a period other than the period that they would be reflected in a non-regulated entity's statements of comprehensive income. Regulatory assets and liabilities are recognized in the Company's statements of comprehensive income in the period that the underlying expenses and income are reflected in the rates charged to shippers and operators. Equitrans, L.P. expects to continue to be subject to rate regulation that will provide for the recovery of deferred costs. The following table summarizes Equitrans, L.P.'s regulatory assets and liabilities that are included in other assets and regulatory and other long-term liabilities, respectively, in the Company's consolidated balance sheets. December 31, 2018 2017 (Thousands) Regulatory assets: Deferred taxes (a) $ 22,252 $ 18,786 Other recoverable costs (b) 4,312 6,165 Total regulatory assets $ 26,564 $ 24,951 Regulatory liabilities: Deferred taxes (a) $ 10,920 $ 11,318 On-going post-retirement benefits other than pension (c) 10,132 7,724 Other reimbursable costs (328 ) 860 Total regulatory liabilities $ 20,724 $ 19,902 (a) The regulatory asset from deferred taxes is primarily related to a historical deferred income tax position and taxes on the equity component of AFUDC. The regulatory liability from deferred taxes relates to the revaluation of a historical difference between the regulatory and tax bases of regulated property, plant and equipment. Equitrans, L.P. expects to recover the amortization of the defe

Rice Energy Merger

Rice Energy Merger	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Rice Energy Merger	Rice Energy Merger As discussed in Note 1 , on November 13, 2017, EQT completed the Rice Merger. EQT recorded the Rice Merger as a business combination using the acquisition method of accounting and performed a preliminary valuation of the fair value of Rice Midstream Holdings' assets and liabilities as of the Rice Merger Date. The fair value of Rice Midstream Holdings' current assets and current liabilities were assumed to approximate their carrying values; as such, their fair values are Level 1 fair value measurements. The estimated fair value of long-lived property, plant and equipment were determined using estimated replacement cost, as adjusted by a usage obsolescence factor. As inputs used in the property, plant and equipment valuation are not observable, the assets' fair values are Level 3 fair value measurements. The fair value of the identified intangible asset was measured using an income approach model that discounts estimated future cash flows using a market-based weighted average cost of capital discount rate. As inputs used in the valuation are not observable, the intangible asset's fair value is a Level 3 fair value measurement. The acquired noncontrolling interest consisted of the third-party ownership interests in RMP and Strike Force Midstream as of the Rice Merger Date. The noncontrolling interest in RMP was calculated using RMP's common unit market price as of the Rice Merger Date. As RMP's common units were actively traded on the New York Stock Exchange, the fair value of the RMP noncontrolling interest is a Level 1 fair value measurement. The noncontrolling interest in Strike Force Midstream was calculated based on the enterprise value of Strike Force Midstream and the ownership percentage not acquired by EQT. As inputs used in the valuation are not observable, the noncontrolling interest's fair value is a Level 3 fair value measurement. See Note 1 for a discussion on fair value measurements. On the Rice Merger Date, Rice Midstream Holdings recorded goodwill of $1,384.9 million to two reporting units within the Gathering segment. In connection with the Separation, EQT transferred to the Company a deferred tax liability assumed in the Rice Merger and a corresponding increase to goodwill of $137.0 million . During the fourth quarter of 2018, the Rice Merger purchase price accounting was finalized and, as a result, the Company recorded a reduction of $20.7 million to goodwill and a corresponding increase of $0.9 million to accounts payable and decrease of $21.6 million to deferred tax liability. The following table summarizes the final purchase price allocation of the fair value of the assets and liabilities of Rice Midstream Holdings as of the Rice Merger Date. These values were recorded by Rice Midstream Holdings through pushdown accounting from EQT. Rice Merger Purchase Price Allocation and Goodwill (Thousands) Enterprise value (a) $ 3,846,240 Fair value of assets acquired and liabilities assumed: Current assets 141,410 Property, plant and equipment 2,265,924 Intangible assets 623,200 Other assets 118 Current liabilities (107,101 ) RMP Credit Facility (266,000 ) Due to EQT (b) (187,742 ) Deferred income taxes (115,456 ) Other long-term liabilities (9,323 ) Total fair value of assets acquired and liabilities assumed 2,345,030 Goodwill (c) 1,501,210 Impairment of goodwill (d) 261,941 Goodwill as of December 31, 2018 $ 1,239,269 (a) Includes the fair value of noncontrolling interests assumed of $1.5 billion and $0.2 billion for RMP and Strike Force Midstream, respectively. (b) At the time of the Rice Merger, EQT repaid $187.5 million of outstanding principal and $0.2 million in accrued interest under Rice Midstream Holdings' revolving credit facility. Following repayment, EQT terminated the Rice Midstream Holdings revolving credit facility agreement. As of December 31, 2017, the $187.7 million is included in accounts payable on the Company's consolidated balance sheet. The Company reimbursed EQT for this amount in 2018. (c) Reflected the value of perceived growth opportunities, synergies and operating leverage anticipated through the acquisition and ownership of the acquired gathering assets as of November 13, 2017. (d) See Note 1 for discussion of the Company's evaluation and recognition of the impairment of goodwill for the year ended December 31, 2018. The Company has unamortized carryover tax basis of $387.1 million of tax-deductible goodwill related to the Rice Merger. Post-Acquisition Operating Results Subsequent to the completion of the Rice Merger, Rice Midstream Holdings contributed the following to the Company's consolidated operating results for the period from November 13, 2017 through December 31, 2017. November 13, 2017 through December 31, 2017 (Thousands) Operating revenues $ 14,881 Operating income attributable to Equitrans Midstream 69,036 Net income attributable to noncontrolling interests 16,644 Net income attributable to Equitrans Midstream 21,814 Unaudited Pro Forma Information The following unaudited pro forma financial information presents the Company's results as though the Rice Merger had been completed at January 1, 2016. The pro forma financial information has been included for comparative purposes and is not necessarily indicative of the results that might have actually occurred had the Rice Merger taken place on January 1, 2016; furthermore, the financial information is not intended to be a projection of future results. Years Ended December 31, 2017 2016 (Thousands) Pro forma operating revenues $ 1,264,704 $ 997,829 Pro forma net income 549,567 440,735 Pro forma net income attributable to noncontrolling interests 445,576 376,284 Pro forma net income attributable to Equitrans Midstream 103,991 64,451

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customers	Revenue from Contracts with Customers As discussed in Note 1 , the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers , on January 1, 2018 using the modified retrospective method of adoption. The Company applied the standard to all open contracts as of the date of initial application. Adoption of the standard did not require an adjustment to the opening balance of equity and did not materially change the amount or timing of the Company's revenues. For the years ended December 31, 2018, 2017 and 2016 , all revenues recognized on the Company's statements of comprehensive income are from contracts with customers. As of December 31, 2018 and 2017 , all receivables recorded on the Company's consolidated balance sheets represent performance obligations that have been satisfied and for which an unconditional right to consideration exists. Gathering, Transmission and Storage Service Contracts The Company provides gathering, transmission and storage services in two manners: firm service and interruptible service. Firm service is provided under firm contracts, which are contracts for gathering, transmission or storage services that generally obligate the customer to pay a fixed, monthly charge to reserve an agreed upon amount of pipeline or storage capacity regardless of the capacity used by the customer during each month. Volumetric-based fees can also be charged under firm contracts for each firm volume transported, gathered or stored as well as for volumes transported, gathered or stored in excess of the firm contracted volume. Interruptible service contracts include volumetric-based fees, which are charges for the volume of gas gathered, transported or stored and generally do not guarantee access to the pipeline or storage facility. These contracts can be short- or long-term. Firm and interruptible contracts are billed at the end of each calendar month, with payment typically due within 21 days. Under a firm contract, the Company has a stand-ready obligation to provide the service over the life of the contract. The performance obligation for firm reservation fee revenue is satisfied over time as the pipeline capacity is made available to the customer. As such, the Company recognizes firm reservation fee revenue evenly over the contract period using a time-elapsed output method to measure progress. The performance obligation for volumetric-based fee revenue is generally satisfied upon the Company's monthly billing to the customer for volumes gathered, transported or stored during the month. The amount billed corresponds directly to the value of the Company's performance to date as the customer obtains value as each volume is gathered, transported or stored. Certain of the Company's gas gathering agreements are structured with minimum volume commitments (MVCs), which specify minimum quantities for which a customer will be charged regardless of quantities gathered under the contract. Revenue is recognized for MVCs when the performance obligation has been met, which is the earlier of when the gas is gathered or when it is remote that the producer will be able to meet its MVC. Water Service Contracts Water service revenues represent fees charged by the Company for the delivery of fresh water to a customer at a specified delivery point and for the collection and recycling or disposal of flowback and produced water. All of the Company's water service revenues are generated under variable price per volume contracts. For fresh water service contracts, the only performance obligation in each contract is for the Company to provide water (usually a minimum daily volume of water) to the customer at a designated delivery point. For flowback and produced water, the performance obligation is collection and disposition of the water, which typically occur within the same day. Water service contracts are billed on a monthly basis, with payment typically due within 21 days. Summary of Disaggregated Revenues The tables below provide disaggregated revenue information by business segment. Year Ended December 31, 2018 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 447,360 $ 356,725 $ — $ 804,085 Volumetric-based fee revenues 549,710 30,076 — 579,786 Water service revenues — — 111,227 111,227 Total operating revenues $ 997,070 $ 386,801 $ 111,227 $ 1,495,098 Year Ended December 31, 2017 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 407,355 $ 348,193 $ — $ 755,548 Volumetric-based fee revenues 102,612 23,793 — 126,405 Water service revenues — — 13,605 13,605 Total operating revenues $ 509,967 $ 371,986 $ 13,605 $ 895,558 Year Ended December 31, 2016 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 339,237 $ 277,816 $ — $ 617,053 Volumetric-based fee revenues 58,257 56,962 — 115,219 Water service revenues — — — — Total operating revenues $ 397,494 $ 334,778 $ — $ 732,272 Summary of Remaining Performance Obligations The following table summarizes the transaction price allocated to the Company's remaining performance obligations under all contracts with firm reservation fees and MVCs as of December 31, 2018 . 2019 2020 2021 2022 2023 Thereafter Total (Thousands) Gathering firm reservation fees $ 476,709 $ 552,636 $ 562,635 $ 562,635 $ 562,635 $ 2,273,123 $ 4,990,373 Gathering revenues supported by MVCs 65,700 71,370 71,175 71,175 71,175 65,700 416,295 Transmission firm reservation fees 351,028 343,984 340,218 335,137 295,243 2,178,736 3,844,346 Total $ 893,437 $ 967,990 $ 974,028 $ 968,947 $ 929,053 $ 4,517,559 $ 9,251,014 Based on total projected contractual revenues, including projected contractual revenues from future capacity expected from expansion projects that are not yet fully constructed for which the Company has executed firm contracts, the Company's firm gathering contracts and firm transmission and storage contracts had weighted average remaining terms of approximately 11 years and 15 years, respectively, as of December 31, 2018 .

Equity

Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Equity	Equity In connection with the Distribution described in Note 1, and based on the 254,586,700 shares of outstanding common stock of EQT (EQT common stock) as of the record date for the Distribution, the Company issued 254,268,864 shares of Equitrans Midstream common stock. As of December 31, 2018 , there were 254,270,971 shares of Equitrans Midstream common stock outstanding, of which EQT owned 50,599,503 . On February 5, 2019 , the Board declared a cash dividend for the fourth quarter of 2018 of $0.41 per share payable on February 27, 2019 to shareholders of record at the close of business on February 15, 2019 . Rights Agreement On November 13, 2018, the Board of Directors of Equitrans Midstream (the Board) declared a dividend of one preferred share purchase right (Right) for each outstanding share of Equitrans Midstream common stock and adopted a shareholder rights plan as set forth in the rights agreement (the Rights Agreement), dated as of November 13, 2018, by and between Equitrans Midstream and American Stock Transfer & Trust Company, LLC, as rights agent. The dividend was paid on November 23, 2018 to Equitrans Midstream shareholders of record as of the close of business on November 23, 2018. The Rights Agreement imposes a significant penalty upon any person or group that acquires 10% (or 15% in the case of a 13G Investor, as defined in the Rights Agreement, or 20% in the case of EQT and a single permitted transferee of the Retained Interest) or more of the outstanding shares of Equitrans Midstream common stock without the approval of the Board. The Rights Agreement will expire on March 31, 2019, unless earlier redeemed by the Company. Upon certain triggering events, each Right would entitle the holder to purchase from the Company one one-hundredth (subject to adjustment) of one share of Series A Junior Participating Preferred Stock, without par value (Preferred Stock), of the Company at an exercise price of $100 (the Exercise Price) per one one-hundredth of a share of Preferred Stock. The following are the potential consequences of a person or group becoming an Acquiring Person, as defined in the Rights Agreement: • Flip In. If a person or group becomes an Acquiring Person, all holders of Rights, except the Acquiring Person, may, for the Exercise Price, purchase shares of Equitrans Midstream common stock with a market value of $200 , based on the market price of Equitrans Midstream common stock prior to such acquisition. • Exchange. After a person or group becomes an Acquiring Person, but before an Acquiring Person owns 50% or more of the outstanding shares of Equitrans Midstream common stock, the Board may extinguish the Rights by exchanging one share of Equitrans Midstream common stock, or an equivalent security, for each Right other than the Rights held by the Acquiring Person . • Flip Over. If the Company is later acquired in a merger or similar transaction after the date that the Rights become exercisable, all holders of Rights, except the Acquiring Person may, for the Exercise Price, purchase shares of the acquiring corporation with a market value of $200 based on the market price of the acquiring corporation's stock prior to such transaction.

Financial Information by Busine

Financial Information by Business Segment	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Financial Information by Business Segment	Financial Information by Business Segment The Company reports its operations in three segments that reflect its three lines of business of Gathering, Transmission and Water. Refer to Note 1 for discussion on business segments. The financial statements include expense allocations for certain corporate functions historically performed by EQT. The financial statements may not include all expenses that would have been incurred had the Company existed as a standalone, publicly traded corporation for the entirety of the periods presented. Years Ended December 31, 2018 2017 2016 (Thousands) Revenues from external customers (including related parties): Gathering $ 997,070 $ 509,967 $ 397,494 Transmission 386,801 371,986 334,778 Water 111,227 13,605 — Total operating revenues $ 1,495,098 $ 895,558 $ 732,272 Operating income (loss): Gathering (a) $ 423,407 $ 369,093 $ 289,643 Transmission 265,579 247,467 238,213 Water 37,667 4,145 — Other (b) (83,569 ) (77,655 ) (62,790 ) Total operating income $ 643,084 $ 543,050 $ 465,066 Reconciliation of operating income to net income: Equity income (c) 61,778 22,171 9,898 Other income 5,011 4,439 27,113 Net interest expense 115,454 34,801 16,761 Income tax expense 83,142 212,402 98,243 Net income $ 511,277 $ 322,457 $ 387,073 (a) Impairment of goodwill of $261.9 million was included in Gathering's operating income for 2018. See Note 1. (b) Other operating loss includes selling, general and administrative expense, separation and other transaction costs and depreciation that are not allocated to the business segments. (c) Equity income is included in the Transmission segment. December 31, 2018 2017 (Thousands) Segment assets: Gathering $ 6,011,654 $ 5,656,094 Transmission (a) 3,066,659 1,947,566 Water 237,602 208,273 Total operating segments 9,315,915 7,811,933 Headquarters, including cash 1,207,920 516,863 Total assets $ 10,523,835 $ 8,328,796 (a) The equity investment in the MVP Joint Venture is included in the Transmission segment. Years Ended December 31, 2018 2017 2016 (Thousands) Depreciation: Gathering $ 98,678 $ 44,957 $ 30,422 Transmission 49,723 58,689 32,269 Water 23,513 3,515 — Other (a) 3,907 (10,487 ) — Total $ 175,821 $ 96,674 $ 62,691 Expenditures for segment assets: Gathering $ 717,251 $ 254,522 $ 295,315 Transmission 114,450 111,102 292,049 Water 23,537 6,233 — Other 29,336 — — Total (b) $ 884,574 $ 371,857 $ 587,364 (a) Depreciation within the Transmission segment for the year ended December 31, 2017 includes a non-cash charge of $10.5 million related to the revaluation of differences between the regulatory and tax bases in Equitrans, L.P.'s regulated property, plant and equipment. For purposes of the Company's consolidated reporting, the $10.5 million is reported in income tax expense with a corresponding reduction to depreciation. (b) The Company accrues capital expenditures when the capital work has been completed but the associated bills have not been paid. Accrued capital expenditures are excluded from the statements of consolidated cash flows until they are paid. Accrued capital expenditures were approximately $109.3 million , $90.7 million , $26.7 million and $24.1 million at December 31, 2018 , 2017 , 2016 and 2015 , respectively. At the Rice Merger Date, the Company assumed $72.3 million of Rice Midstream Holdings accrued capital expenditures.

Investments in Consolidated, No

Investments in Consolidated, Non-Wholly-Owed Entities	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in Consolidated, Non-Wholly-Owed Entities	Investments in Consolidated, Non-Wholly-Owned Entities Investment in EQGP RMP IDR Transaction. On May 22, 2018, pursuant to an IDR purchase and sale agreement dated April 25, 2018, by and among EQT, RMGP and EQGP, EQGP acquired from RMGP all of the issued and outstanding IDRs in RMP in exchange for 36,293,766 common units representing limited partner interests in EQGP (EQGP common units) (the RMP IDR Transaction). EQGP Unit Purchases. On November 29, 2018, the Company entered into written agreements (the Unit Purchase Agreements) with (i) funds managed by Neuberger Berman Investment Adviser LP, pursuant to which the Company acquired 5,842,704 EQGP common units for $20.00 per EQGP common unit (the Purchase Price), (ii) funds managed by Goldman Sachs Asset Management, L.P., pursuant to which the Company acquired 1,865,020 EQGP common units for the Purchase Price, (iii) funds managed by Cushing Asset Management, LP, pursuant to which the Company acquired 920,130 EQGP common units for the Purchase Price, (iv) funds managed by Kayne Anderson Capital Advisors, L.P., pursuant to which the Company acquired 1,363,974 EQGP common units for the Purchase Price, and (v) ZP Energy Fund, L.P., pursuant to which the Company acquired 5,372,593 EQGP common units for the Purchase Price (collectively, the EQGP Unit Purchases). On December 31, 2018, the Company closed on the acquisition of an aggregate 14,560,281 EQGP common units pursuant to the Unit Purchase Agreements (the Initial Unit Purchase Closing) for an aggregate purchase price of $291.2 million . The Initial Unit Purchases Closing resulted in a reduction of additional paid-in capital of $46.8 million and a decrease in noncontrolling interest in consolidated subsidiaries of $244.4 million for the year ended December 31, 2018. As of December 31, 2018, following the Initial Unit Purchase Closing, the Company owned 290,569,047 EQGP common units, representing an approximate 96.1% limited partner interest in EQGP, and the entire non-economic general partner interest in EQGP. Following the Initial Unit Purchase Closing, the Company exercised a limited call right (the Limited Call Right) provided for in Section 15.1(a) of the Second Amended and Restated Agreement of Limited Partnership of EQGP, dated as of October 12, 2018. In January 2019, the Company closed on the acquisition of the remaining EQGP common units not owned by the Company pursuant to the Unit Purchase Agreements and the Limited Call Right. See Note 17 . Investment in EQM Public Offerings of EQM Common Units. During the third quarter of 2015, EQM entered into an equity distribution agreement that established an ATM common unit offering program, pursuant to which a group of managers acting as EQM's sales agents could sell EQM common units having an aggregate offering price of up to $750 million (the $750 Million ATM Program). During the year ended December 31, 2016, EQM issued 2,949,309 EQM common units under the $750 Million ATM Program at an average price per unit of $74.42 . EQM received proceeds from the issuances of $217.1 million , net of underwriters' discount and other offering expenses of $2.4 million , which included commissions of approximately $2.2 million . The $750 Million ATM Program expired in the third quarter of 2018. EQM had no public offerings of its common units during the years ended December 31, 2018 and 2017. Issuances as Drop-Down Transaction and EQM-RMP Mergers Consideration. As described in Note 1 , the Drop-Down Transaction was completed effective May 1, 2018. As part of the consideration for the Drop-Down Transaction, EQM issued 5,889,282 EQM common units to a wholly-owned subsidiary of the Company. On July 23, 2018, in connection with the EQM-RMP Mergers discussed in Note 1 , the 102,323,796 RMP common units then issued and outstanding converted into 33,963,753 EQM common units based on the exchange ratio of 0.3319 , the 36,220 outstanding RMP phantom units fully vested and converted into 12,024 EQM common units based on the exchange ratio of 0.3319 , less applicable tax withholding, and the issued and outstanding IDRs in RMP were canceled. Of the RMP common units issued and outstanding at the time of the EQM-RMP Mergers, the Company owned 28,757,246 RMP common units, which converted into 9,544,530 EQM common units. As of December 31, 2018 , EQGP owned 21,811,643 EQM common units, representing an approximate 17.9% limited partner interest, 1,443,015 EQM general partner units, representing a 1.2% general partner interest, and all of the IDRs in EQM, which entitled EQGP to receive 48.0% of all incremental cash distributions in a quarter after $0.5250 has been distributed to each EQM common and general partner unitholder in that quarter. In addition, as of December 31, 2018 , the Company owned 15,433,812 EQM common units, representing an approximate 12.7% limited partner interest in EQM. See Note 17 for discussion on the EQM IDR Transaction. EQM Cash Distribution. On January 16, 2019 , the Board of Directors of the EQM General Partner declared a cash distribution to EQM's unitholders for the fourth quarter of 2018 of $1.13 per EQM common unit or $211.3 million . On February 13, 2019 , EQM paid the cash distribution to its unitholders of record at the close of business on February 1, 2019 . Cash distributions paid by EQM to the Company were $117.3 million , consisting of $42.1 million with respect to the Company's limited partner interest in EQM, $2.5 million with respect to the Company's general partner interest in EQM and $72.7 million with respect to the Company's IDRs in EQM. Net Changes in Ownership of EQGP and EQM As a result of equity transactions of EQGP and EQM, the Company is required to adjust noncontrolling interest and parent net investment. The following table summarizes the net changes in the Company's parent net investment from changes in the Company's ownership interests in EQGP or EQM for the year ended December 31, 2018 . EQGP and EQM had no equity transactions in 2017, and, as such, there were no changes in the Company's net ownership of EQGP or EQM. During the year ended December 31, 2016, as a result of EQM common units issued under the $750 Million ATM Program and through vestings of long-term incentive plan awards, the Company recorded a gain to parent net investment of approximately $24 million , an increase to deferred tax liability of approximately $16 million and a decrease in noncontrolling interest in consolidated subsidiaries of approximately $40 million . Year Ended December 31, 2018 (Millions) Net changes in parent net investment Drop-Down Transaction $ 16 RMP IDR Transaction (35 ) EQM-RMP Mergers (140 ) Net decrease in parent net investment (159 ) Net decrease in deferred tax liability 56 Net increase in noncontrolling interest in consolidated subsidiaries $ 215 In addition, as discussed above, the EQGP Unit Purchases increased the Company's ownership in EQGP.

Investments in Unconsolidated E

Investments in Unconsolidated Entity	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in Unconsolidated Entity	Investments in Unconsolidated Entity In 2015, EQM assumed EQT's interest in MVP Holdco, LLC (MVP Holdco), an indirect, wholly-owned subsidiary of EQM, which holds the Company's interest in the Mountain Valley Pipeline (the MVP). In January 2016, EQM sold an 8.5% ownership interest in the MVP. The sales of interests in the MVP were for consideration that represented the proportional amount of capital contributions made to the joint venture as of the transaction date. As of December 31, 2018 , EQM is the operator of the MVP and owned a 45.5% interest in the MVP. The MVP Joint Venture is constructing the MVP, an estimated 300 -mile natural gas interstate pipeline that will span from northern West Virginia to southern Virginia. The MVP Joint Venture is a variable interest entity because it has insufficient equity to finance its activities during the construction stage of the project. The Company, through EQM, is not the primary beneficiary of the MVP Joint Venture because the Company does not have the power to direct the activities that most significantly affect the MVP Joint Venture's economic performance. Certain business decisions require a greater than 66 2/3% ownership interest approval, and no one member owns more than a 66 2/3% interest. In April 2018, the MVP Joint Venture announced the MVP Southgate project, a proposed 70 -mile interstate pipeline that will extend from the MVP at Pittsylvania County, Virginia to new delivery points in Rockingham and Alamance Counties, North Carolina. In the fourth quarter of 2018, EQM assumed a portion of Con Edison's ownership interest and purchased a portion of PSNC Energy's ownership interest in the MVP Southgate project for $11.3 million . As a result of these transactions, EQM's ownership interest increased from 32.7% to 47.2% . As of December 31, 2018 , EQM was the operator of the MVP Southgate pipeline and owned a 47.2% ownership interest in the MVP Southgate project. The MVP Joint Venture submitted the MVP Southgate certificate application to the FERC in November 2018. Subject to approval by the FERC, the MVP Southgate project has a targeted in-service date of the fourth quarter 2020. In November 2018 , the MVP Joint Venture issued a capital call notice for the funding of the MVP to MVP Holdco for $167.4 million , of which $143.0 million was paid in January 2019 and $24.4 million is expected to be paid in March 2019 . In addition, in December 2018 , the MVP Joint Venture issued a capital call notice for the funding of the MVP Southgate project to MVP Holdco for $1.8 million , all of which is expected to be paid in March 2019 . The capital contribution payable and the corresponding increase to the investment balance are reflected on the consolidated balance sheet as of December 31, 2018 . The interests in MVP and MVP Southgate are equity method investments for accounting purposes because EQM has the ability to exercise significant influence over the MVP Joint Venture's operating and financial policies. Accordingly, EQM records adjustments to the investment balance for contributions to or distributions from the MVP Joint Venture and for EQM's pro rata share of MVP Joint Venture earnings. Equity income, which is primarily related to EQM's pro rata share of the MVP Joint Venture's AFUDC on the construction of the MVP, is reported in equity income in the Company's statements of comprehensive income. Pursuant to the MVP Joint Venture's limited liability company agreement, EQM is obligated to issue a performance guarantee in favor of the MVP Joint Venture to provide performance assurances of MVP Holdco's obligations to fund its proportionate share of the construction budget for the MVP project. As of December 31, 2018 , the Company's maximum financial statement exposure related to the MVP Joint Venture was approximately $1.7 billion , which consisted of the investment in unconsolidated entity balance on the consolidated balance sheet as of December 31, 2018 and amounts that could have become due under EQM's performance guarantees as of that date. In January 2019, EQM issued a performance guarantee in an amount equal to 33% of EQM's proportionate share of the construction budget for the MVP project, which was $261 million at the time of issuance. The amount of the performance guarantee will decrease based on the capital contributions made by MVP Holdco to the MVP Joint Venture. In addition, in February 2019, EQM issued a performance guarantee of $14 million in favor of the MVP Joint Venture for the MVP Southgate project. Upon the FERC's initial release to begin construction of the MVP Southgate project, EQM's current MVP Southgate performance guarantee will be terminated, and EQM will be obligated to issue a new guarantee in an amount equal to 33% of EQM's proportionate share of the remaining capital obligations for the MVP Southgate project. The following tables summarize the audited financial statements of the MVP Joint Venture. Consolidated Balance Sheets December 31, 2018 2017 (Thousands) Current assets $ 687,657 $ 330,271 Noncurrent assets 3,223,220 747,728 Total assets $ 3,910,877 $ 1,077,999 Current liabilities $ 617,355 $ 65,811 Equity 3,293,522 1,012,188 Total liabilities and equity $ 3,910,877 $ 1,077,999 Statements of Consolidated Operations Years Ended December 31, 2018 2017 2016 (Thousands) AFUDC – equity $ 91,056 $ 32,054 $ 16,315 Net interest income 44,786 16,674 5,206 Net income $ 135,842 $ 48,728 $ 21,521

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Related Party Transactions with EQT EQT remains a related party following the Separation due to its ownership of the Retained Interest. In the ordinary course of business, the Company, through EQM, engaged, and continues to engage, in transactions with EQT and its affiliates, including, but not limited to, gathering agreements, transportation service and precedent agreements, storage agreements and water service agreements. EQGP's, EQM's and RMP's Omnibus Agreements with EQT. Prior to the Separation and Distribution, EQGP, EQM and RMP each had an omnibus agreement with EQT. Pursuant to the omnibus agreements, EQT performed centralized corporate general and administrative services for EQGP, EQM and RMP and provided a license for EQGP's and EQM's use of the name "EQT" and related marks in connection with their businesses. EQGP, EQM and RMP reimbursed EQT for the expenses incurred by EQT in providing these services. EQM and RMP's omnibus agreement also provided for certain indemnification obligations between EQM and EQT. On November 12, 2018, EQT terminated the EQGP, EQM and RMP omnibus agreements. Certain indemnification obligations of EQT, EQM and RMP remain in effect following the termination and have been memorialized pursuant to (i) the amended and restated omnibus agreement, dated November 13, 2018, among EQT, EQM and the EQM General Partner, and (ii) the second amended and restated omnibus agreement, dated November 13, 2018, among EQT, EQT RE, LLC, RM Partners LP (formerly known as Rice Midstream Partners LP), EQM Midstream Management LLC (formerly known as Rice Midstream Management LLC) and EQM Poseidon Midstream LLC (formerly known as Rice Poseidon Midstream LLC). The Company is generally responsible for the surviving obligations of EQT under the Separation and Distribution Agreement. EQGP Working Capital Facility with EQT. See Note 10 . EQM 364 -Day Facility. See Note 10 . Separation and Distribution Agreement. On November 12, 2018, the Company, EQT and EQT Production Company entered into the Separation and Distribution Agreement, pursuant to which, among other things, EQT effected the Separation. The Separation and Distribution Agreement provides for, among other things, indemnification obligations designed to make the Company financially responsible for substantially all liabilities that may exist relating to the Midstream Business, whether incurred prior to or after the Separation. Transition Services Agreement. On November 12, 2018, in connection with the Separation and Distribution, the Company and EQT entered into a transition services agreement (the Transition Services Agreement). Pursuant to the Transition Services Agreement, each party agreed to provide certain services to the other on an interim, transitional basis, including services related to information technology, the administration of certain employee benefits and other corporate support services. The Company and EQT agreed to pay the other a fee for these services on a monthly basis. The Transition Services Agreement will terminate on the expiration of the term of the last service provided under it, which will generally be up to 12 months following the Distribution, subject to each party's right to terminate a service prior to the scheduled expiration date. Tax Matters Agreement. On November 12, 2018, in connection with the Separation and Distribution, the Company and EQT entered into a tax matters agreement (the Tax Matters Agreement) that governs the parties' respective rights, responsibilities and obligations with respect to taxes (including taxes arising in the ordinary course of business and taxes, if any, incurred as a result of any failure of the Distribution and certain related transactions to qualify as generally tax-free for U.S. federal income tax purposes), tax attributes, the preparation and filing of tax returns, the control of audits and other tax proceedings and assistance and cooperation with respect to tax matters. In addition, the Tax Matters Agreement imposes certain restrictions on the Company and its subsidiaries, including restrictions on share issuances, business combinations, sales of assets and similar transactions, that are designed to preserve the tax-free status of the Distribution and certain related transactions. The Tax Matters Agreement provides special rules that allocate tax liabilities in the event that the Distribution, together with certain related transactions, are not tax-free. In general, under the Tax Matters Agreement, each party is expected to be responsible for any taxes, whether imposed on the Company or EQT, that arise from (i) the failure of the Distribution, together with certain related transactions, to qualify for tax-free treatment, or (ii) if certain related transactions were to fail to qualify for their intended tax treatment, in each case, to the extent that the failure to qualify is attributable to actions, events or transactions relating to such party's respective stock, assets or business or a breach of the relevant representations or covenants made by that party in the Tax Matters Agreement. Employee Matters Agreement. On November 12, 2018, in connection with the Separation and Distribution, the Company and EQT entered into an employee matters agreement (the Employee Matters Agreement). Pursuant to the Employee Matters Agreement, the Company and EQT allocated liabilities and responsibilities related to employment and compensation and benefits matters and generally agreed to the Company's assumption of liabilities associated with employees transferred from EQT to the Company in connection with the Separation and Distribution. The Company also agreed to establish certain retirement and welfare plans that mirrored similar plans in effect at EQT, and EQT and the Company agreed to the adjustment and replacement of equity compensation awards denominated in EQT common stock in part with awards denominated in Equitrans Midstream common stock. Shareholder and Registration Rights Agreement. On November 12, 2018, in connection with the Separation and Distribution, the Company entered into a shareholder and registration rights agreement (the Registration Rights Agreement) with EQT, pursuant to which the Company agreed that, upon the request of EQT, the Company will use commercially reasonable efforts to effect the registration of the shares comprising the Retained Interest, and EQT agreed to vote any shares comprising the Retained Interest in proportion to the votes cast by the Company's other shareholders. EQT granted the Company a proxy to vote its shares comprising the Retained Interest in such proportion. The Registration Rights Agreement also includes provisions to facilitate the transferability of the Retained Interest. Related Party Transactions with EQGP and EQM. For the period from November 13, 2018 through December 31, 2018, EQM and EQGP reimbursed the Company for certain expenses related to corporate and general and administrative services provided by the Company pursuant to omnibus agreements between EQM and/or EQGP and the Company. These expenses may not necessarily reflect the actual expenses that EQM or EQGP would have incurred on a stand-alone basis. EQM and EQGP are unable to estimate what those costs would have been on a stand-alone basis. The omnibus agreement between EQGP and the Company was terminated on January 10, 2019. See Note 17. On November 13, 2018, Equitrans Midstream entered into a working capital loan agreement with EQGP (the EQGP Working Capital Facility), through which the Company agreed to make interest-bearing loans available in an aggregate principal amount not to exceed $20 million outstanding at any one time. The EQGP Working Capital Facility was terminated on January 10, 2019. As of December 31, 2018, EQGP had approximately $1 million of borrowings outstanding under the EQGP Working Capital Facility, all of which was forgiven in connection with the termination of the EQGP Working Capital Facility. See note 17. During the period from November 13, 2018 through December 31, 2018, the maximum outstanding borrowing was $3.3 million , the average daily balance was approximately $0.9 million and the weighted average annual interest rate was 4.1% . Summary of Related Party Transactions The following table summarizes the Company's related party transactions. Years Ended December 31, 2018 2017 2016 (Thousands) Operating revenues $ 1,111,289 $ 665,939 $ 551,353 Operating and maintenance expense (a) 49,778 40,601 34,179 Selling, general and administrative expense (a) 85,081 75,610 70,387 Separation and other transaction costs (a) (b) 53,272 85,124 — Equity income 61,778 22,171 9,898 Other income from the Preferred Interest — — 8,293 Interest income from the Preferred Interest 6,578 6,818 1,740 Net interest expense (b) 5 (2,120 ) 3 Net (payments on) proceeds from EQGP's working capital loan with EQT (168 ) 84 18 Capital contributions to the MVP Joint Venture (913,195 ) (159,550 ) (98,399 ) Principal payments received on the Preferred Interest 4,406 4,166 1,024 Net (distributions to) contributions from EQT (701,901 ) (893,682 ) 740,797 (a) Reimbursements to EQT may not necessarily reflect the actual expenses that the Company would have incurred on a standalone basis. The Company is unable to estimate what those expenses would be on a standalone basis. (b) For the years ended December 31, 2018 and 2017 , separation and other transaction costs included charges related to the Rice Merger from EQT of $13.7 million and $85.1 million , respectively. In addition, in 2017, the Company recorded $ 2.9 million in interest expense related to EQT's financing of the Rice Merger that was allocated to the Company from EQT. The basis for allocation of both the Rice Merger transaction costs and interest expense was the relative fair value of Rice Midstream Holdings' net assets acquired by EQT and distributed to the Company in the Rice Merger. See Note 2 . For the year ended December 31, 2018, separation and transaction costs included charges related to the Drop-Down Transaction, the EQM-RMP Mergers and the Separation from EQT of $39.6 million . The basis for allocated separation costs was 50% of such costs incurred by EQT. The following table summarizes the Company's related party receivables and payables. December 31, 2018 2017 (Thousands) Accounts receivable – related parties $ 175,869 $ 158,720 Investment in unconsolidated entity 1,510,289 460,546 Preferred Interest 114,720 119,127 Accounts payable – related parties 34,071 363,058 Capital contribution payable to the MVP Joint Venture 169,202 105,734

Share-based Compensation Plans

Share-based Compensation Plans	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Plans	Share-based Compensation Plans Prior to the Separation, share-based compensation amounts in the accompanying financial statements included phantom stock awards issued to non-employee directors of the EQM General Partner and the EQGP General Partner. In accordance with the Employee Matters Agreement, previously outstanding share-based compensation awards granted under EQT's equity compensation programs prior to the Separation and held by certain executives and employees of the Company and EQT were adjusted to reflect the impact of the Separation on these awards. To preserve the aggregate intrinsic value of EQT awards held prior to the Separation, as measured immediately before and immediately after the Separation, except for EQT option awards (which were converted in accordance with the conversion provisions set forth in the Employee Matters Agreement) each holder of EQT share-based compensation awards generally received an adjusted award consisting of both a share-based compensation award denominated in EQT equity and a share-based compensation award denominated in Company equity. These awards were adjusted accordance with the basket method, resulting in participants retaining one unit of the existing EQT incentive award while receiving an additional 0.8 units of a Company-based award and include awards that will be share-settled and awards expected to be satisfied in cash, which are treated as liability awards. In connection with the Separation, EQT transferred to the Company certain obligations related to the EQT share-based compensation awards outstanding. Subject to certain exceptions, the terms of the underlying long-term incentive programs remain unchanged and are tied to EQT performance metrics and employees' vesting for all awards requires continuous service to their post-Separation employer through the vesting date of the respective awards. The share-based compensation awards that were adjusted and assumed by the Company in connection with the Separation consist primarily of the following programs: Incentive Performance Share Unit Programs, Value Driver Award Programs, Restricted Stock, Restricted Stock Unit awards, deferred share equivalents and Non-Qualified Stock Option awards which are discussed below. Non-employee members of the Board of Directors of the Company and the EQM General Partner receive phantom units in connection with their board service payable in the applicable entity's common equity upon the director's termination of services from the applicable board of directors. The Company is required to recognize share-based compensation expense related to unvested awards held by its employees, no matter which entity settles the obligation. In accordance with the Employee Matters Agreement, the Company will be obligated to settle all outstanding share-based compensation awards denominated in the Company's equity, regardless of whether the holders are employees of the Company or EQT on the vesting date. Likewise, EQT will be obligated to settle all of its outstanding share-based compensation awards denominated in its equity, regardless of whether the holders are employees of the Company or EQT, at the vesting date regardless of whether the holders are employees of EQT or the Company. Changes in performance and the number of outstanding awards can impact the ultimate amount of these obligations. Share-based awards to be settled in Equitrans Midstream common stock upon settlement will be funded by shares acquired by the Company in the open market or from any other person, stock issued directly by the Company or any combination of the foregoing. Share counts for share-based compensation discussed herein represent outstanding shares to be remitted by the Company to its employees and employees of EQT pursuant to the Employee Matters Agreement. The following table summarizes the components of share-based compensation expense for the year ended December 31, 2018. Year Ended December 31, 2018 (Thousands) 2016 EQT Incentive Performance Share Unit Program $ 956 2017 EQT Incentive Performance Share Unit Program 1,642 2018 EQT Incentive Performance Share Unit Program 906 2017 EQT Value Driver Performance Share Unit Award Program 255 2018 EQT Value Driver Performance Share Unit Award Program 2,890 Restricted stock awards 1,048 Non-qualified stock options 201 Other programs, including non-employee director awards 2,678 Total share-based compensation expense $ 10,576 For the years ended December 31, 2017 and 2016 , share-based compensation expense was wholly composed of non-employee director awards of $0.5 million and $0.4 million , respectively. Incentive Performance Share Unit Programs – Equity & Liability Portions of the following Incentive Performance Share Unit Programs were transferred to the Company at the Separation Date: • the 2016 EQT Incentive Performance Share Unit Program (2016 Incentive PSU Program); • the 2017 EQT Incentive Performance Share Unit Program (2017 Incentive PSU Program); and • the 2018 EQT Incentive Performance Share Unit Program (2018 Incentive PSU Program). The 2016 Incentive PSU Program, the 2017 Incentive PSU Program and the 2018 Incentive PSU Program are collectively referred to as the Incentive PSU Programs. The 2016 Incentive PSU Program will vest in equity awards. The 2017 Incentive PSU Program and the 2018 Incentive PSU Program will vest in both equity and liability awards. EQT reported that the Incentive PSU Programs were established to provide long-term incentive opportunities to key employees to further align their interests with those of EQT's shareholders and with the strategic objectives of EQT. The performance period for each of the awards under the Incentive PSU Programs is 36 months, with vesting occurring upon payment following the expiration of the performance period. The Incentive PSU Program awards granted in 2016 and 2017 are earned based on the following: • the level of EQT total shareholder return relative to a predefined peer group; and • the cumulative EQT total sales volume growth, in each case, over the performance period. For the year ended December 31, 2018, the Incentive PSU Program awards granted in 2018 will be earned based on the following: • the level of EQT total shareholder return relative to a predefined peer group; • the level of EQT operating and development cost improvement; and • EQT return on capital employed. For the years ending December 31, 2019 and 2020, the Incentive PSU Program awards will be earned based on new performance goals related to Equitrans Midstream performance to be established by the Company's Management Development and Compensation Committee (the Compensation Committee), subject to continued employment through the payment date. The payout factor varies between zero and 300% of the number of outstanding units contingent on the applicable performance metrics. The Company recorded the 2016 Incentive PSU Program and the portions of the 2017 Incentive PSU Program and the 2018 Incentive PSU Program to be settled in stock as equity awards using a grant date fair value determined through a Monte Carlo simulation, which projects the common stock price of the Company and its peers at the ending point of the performance period. The 2017 Incentive PSU Program and the 2018 Incentive PSU Program also included awards to be settled in cash and, therefore, were recorded at fair value as of the measurement date determined through a Monte Carlo simulation, which projects the common stock price for the Company and its peers at the ending point of the performance period. The expected share prices were generated using each company's annual volatility for the expected term and the commensurate three -year or two -year risk-free rates (each shown in the chart below) for equity awards and liability awards, respectively. As the Incentive PSU Programs include a performance condition that affects the number of shares that will ultimately vest, the Monte Carlo simulation computed the grant date fair value for equity awards or the measurement date fair value for liability awards for each possible performance condition outcome on the grant date for equity awards or the measurement date for liability awards. The Company reevaluates the then-probable outcome at the end of each reporting period to record expense at the probable outcome grant date fair value or measurement date fair value, as applicable. The vesting of the units under each Incentive PSU Program occurs upon payment after the end of the performance period. The following table provides detailed information on each award: Incentive PSU Program Settled In Accounting Treatment Fair Value (a) Risk Free Rate Vested/ Payment Date Awards Paid Value (Millions) Unvested/ Expected Payment Date (b) Awards Outstanding as of December 31, 2018 (c) 2016 Stock Equity $ 109.30 1.31 % N/A N/A N/A First Quarter of 2019 307,553 2017 Stock Equity $ 120.60 1.47 % N/A N/A N/A First Quarter of 2020 35,728 2017 Cash Liability $ 59.90 2.61 % N/A N/A N/A First Quarter of 2020 84,014 2018 Stock Equity $ 76.53 1.97 % N/A N/A N/A First Quarter of 2021 85,872 2018 Cash Liability $ 33.87 2.46 % N/A N/A N/A First Quarter of 2021 100,435 (a) Grant date fair value was determined using a Monte Carlo simulation for equity awards. Fair value was determined using a Monte Carlo simulation as of the measurement date for liability awards. For unvested Incentive PSU Programs, the grant date fair value for equity awards and the measurement date fair value for liability awards is as of December 31, 2018 . The Company recorded compensation expense as of December 31, 2018 using the grant date fair value for equity awards and the measurement date fair value for liability awards, each computed for the outcome that management estimates to be most probable. (b) Vesting will occur upon payment following the expiration of the performance period, subject to continued service through such date. (c) Represents the number of outstanding units as of December 31, 2018 , adjusted for forfeitures. The 2016, 2017 and 2018 Incentive PSU Programs to be settled in stock include 203,238 , 30,112 , and 58,160 shares, respectively, for EQT employees that will be settled by the Company under the Employee Matters Agreement. The 2017 and 2018 Incentive PSU Programs to be settled in cash include 46,297 and 54,643 shares, respectively, for EQT employees that will be settled by the Company under the Employee Matters Agreement. The following table sets forth the total compensation costs capitalized related to the Incentive PSU Programs. Year Ended December 31, 2018 (Thousands) 2016 Incentive PSU Program $ 80.8 2017 Incentive PSU Program (liability only) 1,046.8 2018 Incentive PSU Program (liability only) 304.9 As of December 31, 2018 , $0.3 million , $1.6 million , $0.3 million and $2.2 million of unrecognized compensation cost (assuming no changes to the performance condition achievement level) related to the 2017 Incentive PSU Program – Equity, the 2017 Incentive PSU Program – Liability, the 2018 Incentive PSU Program – Equity and the 2018 Incentive PSU Program – Liability, respectively, was expected to be recognized over the remainder of the performance periods. The following table summarizes the weighted-average assumptions used in the Monte Carlo simulation to estimate fair value: Years Ended December 31, 2018 2017 2016 Accounting Treatment Liability (a) Equity Liability (a) Equity Equity Risk-free rate 2.46 % 1.97 % 2.61 % 1.47 % 1.31 % Dividend yield (b) N/A N/A N/A N/A N/A Volatility factor 35.70 % 32.60 % 41.17 % 32.30 % 28.43 % Expected term 2 Years 3 Years 1 Year 3 Years 3 Years (a) Information shown for the valuation of the liability plan is as of measurement date. (b) Dividends paid from the beginning of the performance period will be cumulatively added as additional shares of common stock. Value Driver Award Programs The 2017 EQT Value Driver Award Program (2017 EQT VDPSU Program) and the 2018 EQT Value Driver Award Program (2018 EQT VDPSU Program) are collectively referred to as the VDPSU Programs. EQT reported that the VDPSU Programs were established to align the interests of key employees with those of EQT's shareholders and with the strategic objectives of EQT. Under the VDPSU Programs, 50% of the awards confirmed vest upon payment following the first anniversary of the grant date and the remaining 50% of the awards confirmed vest upon payment following the second anniversary of the grant date subject to continued service through such date. Due to the graded vesting of each award under the VDPSU Programs, the Company recognized compensation cost over the requisite service period for each separately vesting tranche of the award as though each award was, in substance, multiple awards. The payments are contingent upon EQT's adjusted earnings before interest, income taxes, depreciation and amortization performance as compared to EQT's annual business plan and individual, business unit and Company value driver performance over the respective one -year periods. The following table provides detailed information on each award: EQT VDPSU Program Settled In Accounting Treatment Fair Value per Unit (a) Vested/ Payment Date Cash Paid (Millions) Unvested/ Expected Payment Date Awards Outstanding (Including Accrued Dividends) as of December 31, 2018 (b) 2017 Cash Liability $ 20.02 N/A N/A First Quarter of 2019 170,966 2018 Cash Liability $ 20.02 N/A N/A First Tranche First Quarter of 2019 205,420 N/A N/A N/A Second Tranche First Quarter of 2020 205,781 (a) The fair value per unit is calculated as a weighted average of the Company's and EQT's respective common stock prices on the measurement date. (b) The 2017 and 2018 EQT VDPSU Programs include 94,488 and 194,460 awards, respectively, for EQT employees that will be settled by the Company under the Employee Matters Agreement. The following table sets forth the total compensation costs capitalized related to the VDPSU Programs. Year Ended December 31, 2018 (Thousands) 2017 EQT VDPSU Program $ 955.4 2018 EQT VDPSU Program 1,903.2 Restricted Stock Awards – Equity The restricted stock awards will be fully vested at the end of the three -year period commencing with the date of grant, assuming continued service through such date. As of December 31, 2018 , $2.0 million of unrecognized compensation cost related to non-vested restricted stock equity awards was expected to be recognized over a remaining weighted average vesting term of approximately 1.31 years. A summary of restricted stock equity award activity as of December 31, 2018 , and changes during the year then ended, is presented below. Non-vested Shares (a) Weighted Average Fair Value Aggregate Fair Value Outstanding at January 1, 2018 — $ — $ — Transferred in connection with the Separation 157,000 59.85 9,396,455 Vested (8,383 ) 61.49 (515,448 ) Forfeited (1,245 ) 65.18 (81,149 ) Outstanding at December 31, 2018 147,372 $ 59.71 $ 8,799,858 (a) Non-vested shares outstanding at December 31, 2018 included 66,610 shares for EQT employees that will be settled by the Company once vested under the Employee Matters Agreement. Restricted Stock Unit Awards – Liability In connection with the Separation, EQT transferred 513,413 restricted stock unit liability awards to the Company that will be paid in cash. Adjusting for 3,085 forfeitures, there were 510,328 awards outstanding as of December 31, 2018 . Because these awards are liability awards, the Company records compensation expense based on the fair value of the awards as remeasured at the end of each reporting period. The restricted stock unit awards will be fully vested at the end of the three -year period commencing with the date of original grant, assuming continued service through such date. The total liability recorded for these restricted units was $4.5 million as of December 31, 2018 . Non-vested awards outstanding as of December 31, 2018 included 296,616 awards for EQT employees that will be settled by the Company once vested under the Employee Matters Agreement. Non-Qualified Stock Options In connection with the Separation, EQT transferred stock options to the Company. The fair value of the Company's stock option grants was estimated at the dates of grant using a Black-Scholes option-pricing model. Refer to the table below for assumptions used in the Black-Scholes option-pricing model. Risk-free rates for periods within the contractual life of the option are based on the U.S. Treasury yield curve in effect at the date of grant. Dividend yields are based on the dividend yield of EQT's common stock at the time of grant. Expected volatilities are based on historical volatility of EQT's common stock. Expected term represents the period that options granted are expected to be outstanding based on historical option exercise experience. Years Ended December 31, 2018 2017 2016 Risk-free rate 2.25 % 1.95 % 1.67 % Dividend yield 0.20 % 0.18 % 0.16 % Volatility factor 26.46 % 27.45 % 28.59 % Expected term 5 Years 5 Years 5 Years Options transferred in connection with the Separation 57,440 32,560 105,600 Weighted average grant date fair value $ 8.55 $ 9.89 $ 8.53 Total intrinsic value of options exercised (Millions) $ — $ — $ — As of December 31, 2018 , $0.3 million of unrecognized compensation cost related to outstanding non-vested stock options was expected to be recognized by December 31, 2020. A summary of option activity as of December 31, 2018 , and changes during the year then ended, is presented below. Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at January 1, 2018 — $ — — $ — Transferred in connection with the Separation 464,876 38.55 — — Exercised — — — — Forfeited — — — — Expired — — — — Outstanding at December 31, 2018 464,876 $ 38.55 5.69 Years $ — Exercisable at December 31, 2018 271,311 $ 40.63 2.45 Years $ — Equitrans Midstream Phantom Units The Company grants Equitrans Midstream phantom unit awards to certain non-employee directors. The Equitrans Midstream phantom units vest upon grant, and the value of the Equitrans Midstream phantom units will be paid in Equitrans Midstream common stock upon the directors' termination of service on the Board. The Equitrans Midstream phantom units are accounted for as equity awards; as such, the Company recognizes the fair value of the awards on the grant date as share-based compensation expense upon grant. The Company granted 41,880 Equitrans Midstream phantom units during the year ended December 31, 2018 . The weighted average fair value of the grants, based on the Company's closing common stock price on the business day prior to the grant date, was $21.51 for the year ended December 31, 2018 . EQGP Phantom Units Prior to the completion of the EQGP Buyout, the EQGP General Partner granted phantom unit awards (EQGP phantom units) to certain non-employee directors of the EQGP General Partner. The EQGP phantom units vested upon grant, and the value of the EQGP phantom units were paid in EQGP common units upon the director's termination of service on the EQGP General Partner's Board of Directors. The EQGP phantom units were accounted for as equity awards; as such, EQGP recognized the fair value of the awards on the grant date as share-based compensation expense upon grant. As of December 31, 2018 , there were 21,289 EQGP phantom units, including accrued distributions, outstanding. EQGP granted 10,560 , 8,940 and 8,270 EQGP phantom units during the years ended December 31, 2018, 2017 and 2016 , respectively. The weighted average fair value of the grants, based on EQGP's common unit price on the grant date, was $26.28 , $25.21 and $21.57 for the years ended December 31, 2018, 2017 and 2016 , respectively. EQGP recognized share-based compensation expense of $0.3 million , $0.3 million and $0.2 million for the years ended December 31, 2018, 2017 and 2016 , respectively. In connection with the completion of the EQGP Buyout, the non-employee directors of the EQGP General Partner were paid the Purchase Price for each EQGP phantom unit that they held. See Note 17 . EQM Phantom Units The EQM General Partner has granted phantom unit awards (EQM phantom units) to certain non-employee directors of the EQM General Partner. The EQM phantom units vest upon grant, and the value of the EQM phantom units are paid in EQM common units upon the director's termination of service on the EQM General Partner's Board of Directors. The EQM phantom units are accounted for as equity awards; as such, the Company recognizes the fair value of the awards on the grant date as share-based compensation expense upon grant. As of December 31, 2018 , there were 17,470 EQM phantom units, including accrued distributions, outstanding. EQM granted 5,100 , 2,940 and 2,610 EQM phantom units during the years ended December 31, 2018, 2017 and 2016 , respectively. The weighted average fair value of the grants, based on EQM's common unit price on the grant date, was $68.66 , $76.68 and $75.46 for the years ended December 31, 2018, 2017 and 2016 , respectively. The Company recognized share-based compensation expense of $0.4 million , $0.2 million and $0.2 million for the years ended December 31, 2018, 2017 and 2016 , respectively. RMP Phantom Units Prior to the EQM-RMP Mergers, the RMP General Partner granted phantom unit awards (RMP phantom units) to certain non-employee directors of the RMP General Partner. The RMP phantom units would cliff vest at the end of the requisite service period of approximately one year, and the value of the RMP phantom units were paid in RMP common units upon vesting. The RMP phantom units were equity awards; as such, RMP recognized the fair value of the awards on the grant date as share-based compensation expense on a straight-line basis over the vesting period. On July 23, 2018, in connection with the EQM-RMP Mergers, the 36,220 outstanding RMP phantom units fully vested and converted into 12,024 EQM common units based on the exchange ratio of 0.3319 , less applicable tax withholding. The Company recognized share-based compensation expense of $0.9 million for the period from January 1, 2018 through July 23, 2018.

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt The following table presents the Company's and its affiliates' outstanding debt as of December 31, 2018 and 2017 . December 31, 2018 December 31, 2017 Principal Carrying Value (a) Fair Value (b) Principal Carrying Value (a) Fair Value (b) (Thousands) Equitrans Midstream Credit Facility $ 16,500 $ 16,500 $ 16,500 $ — $ — $ — EQGP Working Capital Facility with EQT — — — 168 168 168 EQM Credit Facility 625,000 625,000 625,000 180,000 180,000 180,000 RMP Credit Facility — — — 286,000 286,000 286,000 Total credit facility borrowings $ 641,500 $ 641,500 $ 641,500 $ 466,168 $ 466,168 $ 466,168 Equitrans Midstream Term Loans $ 600,000 $ 568,105 $ 589,500 $ — $ — $ — EQM 4.00% Senior Notes due 2024 500,000 495,708 479,950 500,000 494,939 504,110 EQM 4.125% Senior Notes due 2026 500,000 493,264 454,200 500,000 492,413 501,990 EQM 4.75% Senior Notes due 2023 1,100,000 1,089,742 1,099,890 — — — EQM 5.50% Senior Notes due 2028 850,000 839,302 841,526 — — — EQM 6.50% Senior Notes due 2048 550,000 538,623 549,566 — — — Total debt 4,100,000 4,024,744 4,014,632 1,000,000 987,352 1,006,100 Less current portion of debt 6,000 6,000 6,000 — — — Total long-term debt $ 4,094,000 $ 4,018,744 $ 4,008,632 $ 1,000,000 $ 987,352 $ 1,006,100 (a) Carrying value of the senior notes and term loans represents principal amount less unamortized debt issuance costs and debt discounts. (b) See Note 1 for a discussion of fair value measurements. The combined aggregate amounts of maturities for long-term debt are as follows: $1.1 billion in 2023 and $3.0 billion in 2024 and thereafter. Equitrans Midstream Credit Facility In October 2018, Equitrans Midstream entered into a credit facility agreement that provides for $100 million in borrowing capacity and matures in October 2023 (the Equitrans Midstream Credit Facility). The Equitrans Midstream Credit Facility is available for general corporate purposes and to fund ongoing working capital requirements. Subject to satisfaction of certain conditions, the Equitrans Midstream Credit Facility has an accordion feature that allows the Company to increase the available borrowings under the facility by up to an additional $200 million . The Equitrans Midstream Credit Facility has a sublimit of up to $25 million for same-day swing line advances and a sublimit of up to $15 million for letters of credit. Under the terms of the Equitrans Midstream Credit Facility, Equitrans Midstream can obtain Base Rate Loans (as defined in the Equitrans Midstream Credit Facility) or Fixed Period Eurodollar Rate Loans (as defined in the Equitrans Midstream Credit Facility) (the Eurodollar Rate Loans). Base Rate Loans are denominated in dollars and bear interest at a base rate plus a margin of 0.75% to 1.25% based on Equitrans Midstream's consolidated leverage ratio. Eurodollar Rate Loans bear interest at a Eurodollar Rate (as defined in the Equitrans Midstream Credit Facility) plus a margin of 1.75% to 2.25% based on Equitrans Midstream's consolidated leverage ratio. In December 2018, Equitrans Midstream entered into an amendment (the Amendment) to the Equitrans Midstream Credit Facility, which amended the Equitrans Midstream Credit Facility to, among other things, permit (i) Equitrans Midstream's entrance into the Term Loan Credit Agreement (defined below), (ii) the EQGP Buyout and the EQM IDR Transaction (defined and discussed in Note 17) and (iii) pari passu liens on the collateral securing the obligations under the Term Loan Credit Agreement and the amended Equitrans Midstream Credit Facility. Loans under the Equitrans Midstream Credit Facility are guaranteed by substantially all of the assets of the Company and the Company's direct and indirect, existing and future, wholly-owned, domestic-restricted subsidiaries, including all of the limited partner interests in EQM and EQGP, subject to certain exceptions and limitations, including the general partner interests in EQM and EQGP. Following the completion of the EQM IDR Transaction (defined and discussed in Note 17), EQGP will no longer be a wholly-owned subsidiary of the Company, and its limited partner interest will no longer guarantee the term loans. The Equitrans Midstream Credit Facility contains negative covenants that, among other things, limit restricted payments, incurrence of debt, dispositions, mergers, fundamental changes and transactions with affiliates. In addition, the Equitrans Midstream Credit Facility contains events of default, including insolvency, nonpayment of scheduled principal or interest obligations, change of control and cross-default related to the acceleration or default of certain other financial obligations, that if occur, could result in termination of the Equitrans Midstream Credit Facility, early payment of amounts outstanding or similar actions. Under the Equitrans Midstream Credit Facility, the Company is required to maintain a consolidated leverage ratio of not more than 3.50 to 1.00, excluding the indebtedness of EQM and its subsidiaries. As of December 31, 2018, EQM had no letters of credit outstanding under the EQM Credit Facility. During the period from November 13, 2018 through December 31, 2018, the maximum outstanding borrowing under the Equitrans Midstream Credit Facility was $16.5 million , the average daily balance was approximately $7.4 million and the weighted average annual interest rate was 4.2% . Equitrans Midstream Term Loan Facility In December 2018, Equitrans Midstream entered into a term loan credit agreement (the Term Loan Credit Agreement) with Goldman Sachs Bank USA, as administrative agent, PNC Bank, National Association, as collateral agent, and the lenders from time to time party thereto, that provides for a senior secured term loan facility in an aggregate principal amount of $600 million and matures in January 2024 (the Term Loans and such facility, the Equitrans Midstream Term Loan Facility). The Company received net proceeds from the Term Loans of $568.1 million , inclusive of a discount of $ 18.0 million and estimated debt issuance costs of $13.9 million . The net proceeds were used to fund the EQGP Buyout, including certain fees, costs and expenses in connection therewith, and the remainder is expected to be used for general corporate purposes. The Term Loans accrue interest equal to one of the following, at Equitrans Midstream's option: (i) an alternate base rate (defined as the greatest of (a) the prime rate, (b) the federal funds effective rate plus 0.50% per annum and (c) one-month London Interbank Offered Rate ( LIBOR ) plus 1.00% per annum), plus an applicable margin of 3.50% per annum, or (ii) LIBOR , plus an applicable margin of 4.50% per annum. The Term Loans are due in equal, quarterly installments in an aggregate annual amount equal to 1.00% of the original principal amount of the Term Loans, or $6 million , with the remaining outstanding balance payable on the maturity date. The current portion of the Term Loans is recorded in Current portion of long-term debt on the consolidated balance sheet. The Term Loan Credit Agreement requires Equitrans Midstream to prepay outstanding Term Loans, subject to certain exceptions, with Net Proceeds (as defined in the Term Loan Credit Agreement) from certain non-ordinary course dispositions of assets or from the issuance or incurrence of debt obligations for borrowed money not permitted under the Term Loan Credit Agreement and certain other debt obligations for borrowed money, and, beginning on March 31, 2019 (but suspended during the continuance of either the Company or the Term Loans obtaining and maintaining an investment grade rating from two of S&P, Moody's and Fitch, in each case with a stable or better outlook), a variable percentage of excess cash flow, ranging from 50% to 0% depending on the Company's consolidated net leverage ratio. The Term Loans are guaranteed by substantially all of the assets of the Company and the Company's direct and indirect, existing and future, wholly-owned, domestic-restricted subsidiaries, including all of the limited partner interests in EQM and EQGP, subject to certain exceptions and limitations, including the general partner interests in EQM and EQGP. The Term Loan Credit Agreement contains negative covenants that, among other things, limit the Company's and its subsidiaries' abilities to incur indebtedness or make guarantees of indebtedness; incur liens; make investments, loans and acquisitions; merge or consolidate; sell assets and issue equity interests; pay dividends on capital stock or redeem, repurchase or retire capital stock, subject to exceptions; alter the Company's business; engage in transactions with affiliates; enter into agreements limiting subsidiary distributions; and enter into certain hedging transactions. In addition, the Term Loan Credit Facility contains events of default, including insolvency, nonpayment of scheduled principal or interest obligations, change of control and cross-default related to the acceleration or default of certain other financial obligations, that if occur, could result in termination of the Equitrans Midstream Credit Facility, early payment of amounts outstanding or similar actions. Under the Term Loan Credit Agreement, the Company is required to maintain a debt service coverage ratio of not more than 1.10 to 1.00 beginning with the fiscal quarter ended on March 31, 2019 (but suspended during the continuance of either the Company or the Term Loans obtaining and maintaining an investment grade rating from two of S&P, Moody's and Fitch, in each case with a stable or better outlook). In addition to permitting the EQGP Buyout, the Term Loan Credit Agreement permits, subject to limited conditions, transactions contemplated by any definitive agreements related to the EQM IDR Transaction (defined and discussed in Note 17). The Term Loan Credit Agreement provides the Company with the right to request incremental term loans in an aggregate amount of up to $150 million minus the aggregate commitments under the Equitrans Midstream Credit Facility (or any other permitted pari passu revolving credit agreement then in effect), plus the amount of any voluntary prepayment in respect of the Term Loans. The lenders under the Term Loan Credit Agreement are under no obligation to provide such incremental commitments or term loans and any addition of or increase in commitments or term loans is subject to certain customary conditions precedent. EQGP Working Capital Facility with EQT Prior to the Separation, EQGP had a working capital loan agreement with EQT (the EQGP Working Capital Facility with EQT), through which EQT agreed to make interest-bearing loans available in an aggregate principal amount not to exceed $50 million outstanding at any one time. Borrowings outstanding under the EQGP Working Capital Facility with EQT were presented in accounts payable as an amount due to related party on the consolidated balance sheets. On November 12, 2018, EQGP repaid $3.2 million of borrowings outstanding under the facility, and EQT terminated the working capital loan agreement. During the period from January 1, 2018 through November 12, 2018, the maximum outstanding borrowing was $3.2 million , the average daily balance was approximately $0.2 million and the weighted average annual interest rate was 3.5% . During the years ended December 31, 2017 and 2016 , the maximum outstanding borrowings were $0.3 million and $0.2 million , respectively, the average daily balance for each period was $0.1 million and the weighted average annual interest rates were 2.5% and 2.0% , respectively. EQM Credit Facility In October 2018, EQM amended and restated its credit facility to increase the borrowing capacity from $1 billion to $3 billion and extend the term to October 2023 (the EQM Credit Facility). The EQM Credit Facility is available for general partnership purposes, including to purchase assets, and to fund working capital requirements and capital expenditures, pay distributions and repurchase units. Subject to satisfaction of certain conditions, the EQM Credit Facility has an accordion feature that allows EQM to increase the available borrowings under the facility by up to an additional $750 million . The EQM Credit Facility has a sublimit of up to $250 million for same-day swing line advances and a sublimit of up to $400 million for letters of credit. In addition, EQM has the ability to request that one or more lenders make available term loans under the EQM Credit Facility, subject to the satisfaction of certain conditions. Such term loans would be secured by cash and qualifying investment grade securities. EQM's obligations under the revolving portion of the EQM Credit Facility are unsecured. EQM's debt issuer credit ratings determine the level of fees associated with the EQM Credit Facility and the interest rate charged by the counterparties on amounts borrowed against the lines of credit. EQM's debt credit rating and level of fees and interest rates are inversely related. Under the terms of the EQM Credit Facility, EQM can obtain Base Rate Loans (as defined in the EQM Credit Facility) or Fixed Period Eurodollar Rate Loans (as defined in the EQM Credit Facility) (Eurodollar Rate Loans). Base Rate Loans are denominated in dollars and bear interest at a base rate plus a margin of 0.125% to 0.875% determined on the basis of EQM's then current credit rating. Eurodollar Rate Loans bear interest at a Eurodollar Rate (as defined in the EQM Credit Facility) plus a margin of 1.125% to 1.875% determined on the basis of EQM's then current credit rating. EQM may voluntarily prepay its borrowings, in whole or in part, without premium or penalty, but subject to reimbursement of funding losses with respect to prepayment of Eurodollar Rate Loans. The EQM Credit Facility contains negative covenants that, among other things, limit restricted payments, incurrence of debt, dispositions, mergers and fundamental changes and transactions with affiliates. In addition, the EQM Credit Facility contains events of default such as insolvency, nonpayment of scheduled principal or interest obligations, change of control and cross-default related to the acceleration or default of certain other financial obligations. Under the EQM Credit Facility, EQM is required to maintain a consolidated leverage ratio of not more than 5.00 to 1.00 (or not more than 5.50 to 1.00 for certain measurement periods following the consummation of certain acquisitions). As of December 31, 2018 , EQM had $1 million of letters of credit outstanding under the EQM Credit Facility. As of December 31, 2017 , EQM had no letters of credit outstanding under the EQM Credit Facility. During the years ended December 31, 2018, 2017 and 2016 , the maximum outstanding borrowings were $674 million , $260 million and $401 million , respectively; the average daily balances were approximately $230 million , $74 million and $77 million , respectively; and the weighted average annual interest rates were 3.6% , 2.8% and 2.0% , respectively. For the years ended December 31, 2018, 2017 and 2016, commitment fees of $2.8 million , $1.8 million and $1.6 million , respectively, were paid to maintain credit availability under the EQM Credit Facility. EQM 364 -Day Facility Prior to the Separation, EQM had a $500 million , 364 -day, uncommitted revolving loan agreement with EQT (the EQM 364 -Day Facility ) . Interest accrued on outstanding borrowings at an interest rate equal to the rate then applicable to similar loans under the revolving credit agreement with the largest aggregate commitment amount to which EQM was then a party, less the sum of (i) the then applicable commitment fee under such agreement and (ii) 10 basis points. On November 12, 2018, EQT terminated the EQM 364 -Day Facility. EQM had no borrowings outstanding under the EQM 364-Day Facility as of December 31, 2017. There were no borrowings outstanding at any time during the period from January 1, 2018 through November 12, 2018 or the year ended December 31, 2016. During the year ended December 31, 2017, under the EQM 364 -Day Facility, the maximum outstanding borrowing was $100.0 million , the average daily balance was approximately $23 million and the weighted average annual interest rate was 2.2% . EQM Term Loan Facility In April 2018, EQM entered into a $2.5 billion unsecured multi-draw 364 -day term loan facility (the EQM Term Loan Facility). The EQM Term Loan Facility was used to fund the cash consideration for the Drop-Down Transaction, to repay borrowings under EQM's then-existing revolving credit facility and for other general partnership purposes. In connection with EQM's issuance of the EQM $2.5 Billion Senior Notes (defined below), on June 25, 2018, the outstanding balance under the EQM Term Loan Facility was repaid and the EQM Term Loan Facility was terminated. As a result of the termination, EQM expensed $3 million of deferred issuance costs. Under the EQM Term Loan Facility, from April 25, 2018 through June 25, 2018, the maximum outstanding borrowing was $1,825 million , the average daily balance was approximately $1,231 million , and the weighted average annual interest rate was 3.3% . EQM $2.5 Billion Senior Notes In June 2018, EQM issued 4.75% senior notes due July 2023 in the aggregate principal amount of $1.1 billion , 5.50% senior notes due July 2028 in the aggregate principal amount of $850 million and 6.50% senior notes due July 2048 in the aggregate principal amount of $550 million (collectively, the EQM $2.5 Billion Senior Notes). EQM received net proceeds from the offering of $2,465.8 million , inclusive of a discount of $11.8 million and estimated debt issuance costs of $22.4 million . The net proceeds were used to repay the outstanding balances under the EQM Term Loan Facility and the RMP Credit Facility (defined below), and the remainder was used for general partnership purposes. The EQM $2.5 Billion Senior Notes were issued pursuant to new supplemental indentures to EQM's existing indenture dated August 1, 2014. The EQM $2.5 Billion Senior Notes contain covenants that limit EQM's ability to, among other things, incur certain liens securing indebtedness, engage in certain sale and leaseback transactions and enter into certain consolidations, mergers, conveyances, transfers or leases of all or substantially all of EQM's assets. EQM 4.125% and 4.00% Senior Notes In the fourth quarter of 2016, EQM issued $500 million aggregate principal amount of 4.125% senior notes due December 2026 (the 4.125% Senior Notes). EQM used the net proceeds from the offering to repay the then outstanding borrowings under the EQM Credit Facility and for general partnership purposes. In the third quarter of 2014, EQM issued $500 million aggregate principal amount of 4.00% senior notes due August 2024 (the 4.00% Senior Notes). EQM used the net proceeds from the offering to repay the outstanding borrowings under the EQM Credit Facility and for general partnership purposes. Both the 4.125% Senior Notes and the 4.00% Senior Notes contain covenants that limit EQM's ability to, among other things, incur certain liens securing indebtedness, engage in certain sale and leaseback transactions and enter into certain consolidations, mergers, conveyances, transfers or leases of all or substantially all of EQM's assets. RMP Credit Facility RM Operating LLC (formerly Rice Midstream OpCo LLC), a wholly-owned subsidiary of RMP, had an $850 million credit facility (the RMP Credit Facility) that was terminated on July 23, 2018 in conjunction with the EQM-RMP Mergers. Prior to its termination, the RMP Credit Facility was available for general partnership purposes, including to purchase assets, and to fund working capital requirements and capital expenditures, pay distributions and repurchase units. As of December 31, 2017 , RM Operating LLC had $1 million of letters of credit outstanding under the RMP Credit Facility. Under the RMP Credit Facility, for the period from January 1, 2018 through July 23, 2018, the maximum outstanding borrowing was $375 million , the average daily balance was approximately $300 million and the weighted average interest rate was 3.8% . For the period from November 13, 2017 through December 31, 2017 , the maximum outstanding borrowing was $286 million , the average daily balance was approximately $268 million and the weighted average interest rate was 3.1% . As of December 31, 2018 , the Company and EQM were in compliance with all debt provisions and covenants.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table summarizes income tax expense for the years ended December 31, 2018, 2017 and 2016 . Years Ended December 31, 2018 2017 2016 (Thousands) Current income tax expense: Federal $ 41,788 $ 43,794 $ 94,068 State 16,108 10,239 21,751 Total current income tax expense 57,896 54,033 115,819 Deferred income tax expense (benefit): Federal 96,499 148,623 (7,892 ) State (71,253 ) 9,746 (9,684 ) Total deferred income tax expense (benefit) 25,246 158,369 (17,576 ) Total income tax expense $ 83,142 $ 212,402 $ 98,243 The following table summarizes differences between income tax expense and amounts computed at the applicable federal statutory rate on pre-tax income for the years ended December 31, 2018, 2017 and 2016 . Years Ended December 31, 2018 2017 2016 (Thousands) Income tax expense at statutory rate $ 124,828 $ 187,201 $ 169,860 Tax Reform Legislation 7,443 129,266 — State income tax expense 21,827 12,710 7,844 Noncontrolling interests' share of earnings (61,505 ) (116,539 ) (112,672 ) Impairment of goodwill 16,535 — — Rice Midstream Holdings income not subject to tax (26,538 ) (13,460 ) — Regulatory (asset) liability (368 ) 10,488 35,438 Other 920 2,736 (2,227 ) Income tax expense $ 83,142 $ 212,402 $ 98,243 Effective tax rate 14.0 % 39.7 % 20.2 % On December 22, 2017, the U.S. Congress enacted the Tax Reform Legislation, which made significant changes to U.S. federal income tax law, including lowering the federal corporate tax rate to 21% from 35% beginning January 1, 2018. As of December 31, 2018, the Company completed its accounting for the effects of the Tax Reform Legislation, including accounting for the revaluation of net deferred tax assets and for state income tax effects, and recorded deferred income tax expense of $7.5 million , which is in addition to the $129.3 million of deferred income tax expense recorded during the year ended December 31, 2017. The Company also considered whether existing deferred tax assets will be recovered in future periods under this legislation and noted no significant effect on the deferred tax assets. For the years ended December 31, 2018, 2017 and 2016, the effective tax rates were reduced from the federal and statutory rates because the Company did not record income tax expense on the portions of its income attributable to the noncontrolling limited partners of EQGP and EQM and, for the period prior to July 23, 2018 and May 1, 2018, attributable to the noncontrolling limited partners of RMP and Gulfport Midstream's 25% interest in Strike Force Midstream, respectively. Prior to October 22, 2018, Rice Midstream Holdings was a multi-member limited liability company; therefore, the earnings of Rice Midstream Holdings and its subsidiaries were not subject to federal income tax. In the fourth quarter of 2018, Rice Midstream Holdings was merged out of existence as part of internal restructurings. For the year ended December 31, 2017 , the Company recorded a $10.5 million tax expense related to Equitrans, L.P.'s FERC-regulated assets as a result of the corporate tax rate reduction in the Tax Reform Legislation. Following the normalization rules of the Internal Revenue Code (IRC), this regulatory liability is amortized on a straight-line basis over the estimated remaining life of the related assets. The following table summarizes the components of net deferred tax assets. December 31, 2018 2017 (Thousands) Total deferred income tax asset: Net operating loss carryforwards $ 36,202 $ — Investment in partnerships 559,858 257,128 Other 1,261 — Total excluding valuation allowance 597,321 257,128 Valuation allowance — — Total net deferred income tax asset $ 597,321 $ 257,128 The Company has federal and state Net Operating Loss (NOL) carryforwards related to federal and various state jurisdictions. The federal and West Virginia NOL carryforwards have no expiration, but utilization is limited to 80% of taxable income in the year of utilization. Other state NOL carryforwards expire in 2038. The Company believes that it is more likely than not that the benefit from certain federal and state NOL carryforwards will be realized. In addition to the NOL carryforwards, the Company has recorded deferred tax assets principally resulting from its investment in partnerships. No valuation allowances have been established, as it is believed that future sources of taxable income, reversing temporary differences and other tax planning strategies will be sufficient to realize these deferred tax assets. Any determination to change the valuation allowance would impact the Company's income tax expense and net income in the period in which such a determination is made. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not (greater than 50% ) that a tax benefit will not be realized. In evaluating the need for a valuation allowance, management considers all potential sources of taxable income, including income available in carry-back periods, future reversals of taxable temporary differences, projections of taxable income and income from tax planning strategies, as well as all available positive and negative evidence. Positive evidence includes factors such as a history of profitable operations, projections of future profitability within the carry-forward period, including from tax planning strategies, and experience. No significant negative evidence has been noted. Deferred tax assets for which no valuation allowance is recorded may not be realized and changes in facts and circumstances may result in the establishment of a valuation allowance. Existing valuation allowances are re-examined under the same standards of positive and negative evidence that apply to valuation allowance establishment. If it is determined that it is more likely than not that a deferred tax asset for which a valuation is recorded will be realized, all or a portion of the valuation allowance may be released. Deferred tax assets and liabilities are also re-measured to reflect changes in underlying tax rates from law changes. The Company has not identified any uncertain tax positions as of December 31, 2018 and 2017 .

Concentrations of Credit Risk

Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Concentrations of Credit Risk	Concentrations of Credit Risk For the years ended December 31, 2018, 2017 and 2016 , EQT accounted for approximately 74% , 74% and 75% , respectively, of the Company's total revenues across all of the Company's operating segments. Additionally, for the years ended December 31, 2018, 2017 and 2016 , PNG Companies LLC and its affiliates accounted for approximately 7% , 11% and 12% , respectively, of the Company's total revenues. As of December 31, 2018 and 2017 , approximately 51% and 39% , respectively, of the accounts receivable balances represented amounts due from marketers excluding EQT. To manage the credit risk related to transactions with marketers, the Company engages with only those that meet specified criteria for credit and liquidity strength and actively monitors accounts with marketers. In connection with its assessment of marketer credit and liquidity strength, the Company may request a letter of credit, guarantee, performance bond or other credit enhancement. The Company did not experience significant defaults on accounts receivable during the years ended December 31, 2018 , 2017 and 2016 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Equitrans Midstream Corporation is not currently a party to any legal proceedings; however, in the ordinary course of business, various legal and regulatory claims and proceedings are pending or threatened against EQM and its subsidiaries. While the amounts claimed may be substantial, EQM is unable to predict with certainty the ultimate outcome of such claims and proceedings. EQM accrues legal and other direct costs related to loss contingencies when incurred. EQM establishes reserves whenever it believes it to be appropriate for pending matters. Furthermore, after consultation with counsel and considering available insurance, EQM believes that the ultimate outcome of any matter currently pending against EQM will not materially affect its business, financial condition, results of operations, liquidity or ability to make quarterly cash distributions to EQM unitholders, including the Company. EQM is subject to federal, state and local environmental laws and regulations. These laws and regulations, which are constantly changing, can require expenditures for remediation and, in certain instances, can result in assessment of fines. EQM has established procedures for the ongoing evaluation of its operations to identify potential environmental exposures and to ensure compliance with regulatory requirements. The estimated costs associated with identified situations requiring remedial action are accrued; however, when recoverable through future regulated rates, certain of these costs are deferred as regulatory assets. Ongoing expenditures for compliance with environmental laws and regulations, including investments in facilities to meet environmental requirements, have not been material. Management believes that any such required expenditures will not be significantly different in either nature or amount in the future and does not know of any environmental liabilities that will have a material effect on EQM's business, financial condition, results of operations, liquidity or ability to make quarterly cash distributions to EQM's unitholders, including the Company. The Company has identified situations that require remedial action for which approximately $2.1 million is included in other liabilities and credits on the consolidated balance sheets as of December 31, 2018. For the years ended December 31, 2018, 2017 and 2016, operating lease rental payments for office locations and warehouse buildings, as well as for a limited number of compressors, were $7.2 million , $5.4 million and $4.7 million , respectively. Future lease payments under non-cancelable operating leases and compressors as of December 31, 2018 totaled $68.4 million (2019 – $7.2 million , 2020 – $6.3 million , 2021 – $6.2 million , 2022 – $6.2 million , 2023 – $6.0 million and 2024 and thereafter – $36.5 million ). EQM has a water system expansion and supply agreement with Southwestern Pennsylvania Water Authority (SPWA) (SPWA Agreement), pursuant to which EQM agreed to fund and assist SPWA in its construction and expansion of a water supply system that serves parts of Greene, Fayette and Washington Counties in Pennsylvania. In exchange, SPWA granted EQM preferred rights to water volumes supplied through the system for use in EQM's business. EQM is also entitled to a surcharge of $3.50 per 1,000 gallons of water sold assessed by SPWA against customers that use the system. All facilities and improvements that are constructed pursuant to the SPWA Agreement are the property of SPWA. To date, EQM authorized expenditures of approximately $29.5 million and funded expenditures of $13.4 million and $11.7 million during the years ended December 31, 2018 and 2017 , respectively. As of December 31, 2018, EQM had a remaining commitment of approximately $0.8 million associated with these authorizations. See Note 7 for discussion of the MVP Joint Venture guarantees.

Post-retirement Benefit Plans

Post-retirement Benefit Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Post-retirement Benefit Plans	Post-retirement Benefit Plans Prior to the Separation and Distribution, employees of EQT operated the Company's and EQM's assets. EQT charged the Company for the payroll and benefit costs associated with these individuals and for the retirees of Equitrans, L.P. Post-Separation, employees of the Company operate EQM's assets. The Company charges EQM for the payroll and benefit costs associated with these individuals and for the retirees of Equitrans, L.P. The Company carries obligations for employee-related benefits in its financial statements. In 2014, EQT terminated the Retirement Plan. Prior to its termination, the retirees of Equitrans, L.P. participated in the Retirement Plan. On March 2, 2016, the IRS issued a favorable determination letter for the termination of the Retirement Plan. On June 28, 2016, EQT purchased annuities from, and transferred the Retirement Plan assets and liabilities to, American General Life Insurance Company. In the third quarter of 2016, the Company reimbursed EQT $5.2 million for its proportionate share of the funding related to the retirees of Equitrans, L.P. The settlement charge is expected to be recoverable in FERC-approved rates and, thus, was recorded as a regulatory asset that will be amortized for rate recovery purposes over a period of 16 years . Excluding the Retirement Plan termination settlement described above, for the year ended December 31, 2016, the Company reimbursed EQT $1.9 million for the funding of the Retirement Plan and was allocated expenses associated with the Retirement Plan of $0.1 million . Upon Separation, EQT transferred to the Company the post-retirement benefits liability and accumulated other comprehensive income balance associated with the Retirement Plan. The Company recognizes expense for on-going post-retirement benefits other than pension, a portion of which is subject to recovery in the approved rates of Equitrans, L.P.'s rate-regulated business. Prior to the Separation, the Company contributed to a defined contribution plan sponsored by EQT. The contribution amount was equal to a percentage of allocated base salary. During the period from January 1, 2018 through November 12, 2018 and for the years ended December 31, 2017 and 2016, the Company was charged its contribution percentage through the EQT payroll and benefit costs discussed in Note 8 . For the period from the Separation Date through December 31, 2018, the Company recognized expense related to its defined contribution plan of $0.6 million . The Company recognizes expenses for ongoing post-retirement benefits other than pensions, which are subject to recovery in FERC-approved rates. Expenses recognized by the Company for ongoing post-retirement benefits other than pensions were approximately $1.2 million for each year ended December 2018, 2017 and 2016.

Interim Financial Information (

Interim Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Interim Financial Information (Unaudited)	Interim Financial Information (Unaudited) The following quarterly summary of operating results reflects variations due primarily to the effect of the Tax Reform Legislation in the three months ended December 31, 2017, the effect of the Rice Merger for the period from November 13, 2017 through December 31, 2018, the effect of increasing separation and other transaction costs related to the EQM-RMP Mergers, the Drop-Down Transaction, the Separation and the EQGP Buyout, the $261.9 million of impairment of goodwill recorded in the fourth quarter of 2018 and the seasonal nature of the Company's transmission and storage business. Three Months Ended March 31 (a) June 30 (a) September 30 (a) December 31 (a)(b) (Thousands, except per share amounts) 2017 Operating revenues $ 200,072 $ 196,815 $ 206,293 $ 292,378 Operating income 144,096 139,178 141,282 118,494 Net income (loss) 118,982 115,885 115,451 (27,861 ) Net income (loss) attributable to Equitrans Midstream 32,269 34,366 33,334 (127,125 ) Earnings (loss) per share of common stock attributable to Equitrans Midstream Basic: Weighted average common stock outstanding 254,432 254,432 254,432 254,432 Net income (loss) $ 0.13 $ 0.14 $ 0.13 $ (0.50 ) Diluted: Weighted average common stock outstanding 255,033 255,033 255,033 254,432 Net income (loss) $ 0.13 $ 0.13 $ 0.13 $ (0.50 ) Three Months Ended March 31 (a) June 30 (a) September 30 (a) December 31 (b) (Thousands, except per share amounts) 2018 Operating revenues $ 371,026 $ 374,697 $ 364,584 $ 384,791 Operating income (loss) 249,340 234,868 218,322 (59,446 ) Net income (loss) 223,744 219,607 185,966 (118,040 ) Net income (loss) attributable to Equitrans Midstream 82,729 101,067 82,825 (48,223 ) Earnings (loss) per share of common stock attributable to Equitrans Midstream Basic: Weighted average common stock outstanding 254,432 254,432 254,432 254,432 Net income (loss) $ 0.33 $ 0.40 $ 0.33 $ (0.19 ) Diluted: Weighted average common stock outstanding 255,033 255,033 255,033 254,432 Net income (loss) $ 0.32 $ 0.40 $ 0.32 $ (0.19 ) (a) For periods prior to the Separation Date, EPS was calculated based on the shares of Equitrans Midstream common stock distributed in connection with the Separation and Distribution and is considered pro forma in nature. Prior to the Separation Date, the Company did not have any issued or outstanding common stock (other than shares owned by EQT). (b) For the quarters ended December 31, 2018 and 2017, because the Company generated a net loss, the Company's computation of EPS excluded potentially dilutive securities; as such, basic and diluted weighted average common stock outstanding were the same for the quarters ended December 31, 2018 and 2017.

Consolidated Variable Interest

Consolidated Variable Interest Entities	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidated Variable Interest Entities	Consolidated Variable Interest Entities As of December 31, 2018, EQGP and EQM were variable interest entities. Through the Company's ownership and control of the EQGP General Partner and the EQM General Partner, the Company had the power to direct the activities that most significantly affected EQGP's and EQM's economic performance during the periods presented. Through its limited partner interests in EQGP and EQM and through EQGP's general partner interest, limited partner interest and IDRs in EQM, the Company had the right to receive benefits from, as well as the obligation to absorb the losses of, EQGP and EQM. As the Company is the primary beneficiary of and has a controlling financial interest in EQGP and EQM, the Company consolidated EQGP, which consolidated EQM for the periods presented. In addition, for discussion of related party transactions, see Note 8 . Following the completion of the EQGP Buyout, EQGP became an indirect, wholly-owned subsidiary of the Company. See Note 17 . Significant risks associated with EQM include, without limitation, the following: • The Company's only cash-generating assets are its partnership interests in EQM; as such, the Company's cash flow is dependent on EQM cash distributions. • Given EQM's expectation that it will derive a substantial majority of its revenues from EQT for the foreseeable future, any event, whether in EQM's areas of operations or otherwise, that adversely affects EQT's production, financial condition, leverage, results of operations or cash flows may adversely affect EQM's ability to sustain or increase cash distributions to its unitholders, including the Company; • Gathering, transmission and water services are subject to extensive regulation, environmental and otherwise, by federal, state and local authorities, which may expose EQM to significant costs and liabilities; • Expanding EQM's business through construction of midstream assets subjects EQM to risks. If EQM does not complete its planned expansion projects on schedule, at the budgeted cost or at all, its business, financial condition, results of operations, liquidity and ability to make quarterly cash distributions to its unitholders, including the Company, may be adversely affected and Company's and EQM's future growth may be limited; • EQM is subject to hazards and operational risks, including, but not limited to, ruptures, fires, explosions and leaks to pipelines, facilities, equipment and surrounding properties caused by natural disasters, adverse weather, acts of sabotage and terrorism and inadvertent error; and • Certain services EQM provides on its transmission and storage system are subject to long-term, fixed-price negotiated rate contracts that are not subject to adjustment, regardless of whether EQM's cost to perform such a service exceeds the revenues received; as a result, EQM's costs could exceed the revenues received. The following table presents assets and liabilities included in the Company's consolidated balance sheets that were for the use or obligation of EQM, inclusive of receivables and payables due from or to related parties. December 31, 2018 2017 (a) (Thousands) ASSETS Cash and cash equivalents $ 17,515 $ 2,557 Accounts receivable (a) 254,390 132,108 Other current assets 14,909 12,662 Net property, plant and equipment 5,806,628 2,804,059 Investment in unconsolidated entity 1,510,289 460,546 Goodwill 1,123,813 — Net intangible assets 576,113 — Other assets 152,464 136,895 LIABILITIES Accounts payable (a) $ 207,877 $ 78,713 Capital contribution payable to the MVP Joint Venture 169,202 105,734 Accrued interest 80,199 10,926 Accrued liabilities 20,672 16,871 Credit facility borrowings 625,000 180,000 EQM Senior notes 3,456,639 987,352 Regulatory and other long-term liabilities 38,724 20,273 (a) Amounts as of December 31, 2017 have not been recast to include the results of the EQM-RMP Mergers and Drop-Down Transaction. (b) Accounts receivable and accounts payable as of December 31, 2018 and 2017 included $174.8 million and $103.3 million , respectively, of receivables due from EQT and $34.0 million and $31.7 million , respectively, of payables due to EQT that were for the use or obligation of EQM, respectively, on that date. The following table summarizes EQM's statements of consolidated operations and cash flows, inclusive of transactions with related parties. Years Ended December 31, 2018 2017 (a) 2016 (Thousands) Operating revenues $ 1,495,098 $ 826,522 $ 732,272 Operating expenses 768,445 245,032 204,416 Other (expenses) income (55,305 ) (9,586 ) 10,098 Net income $ 671,348 $ 571,904 $ 537,954 Net cash provided by operating activities $ 1,187,239 $ 650,550 $ 537,904 Net cash used in investing activities (2,950,254 ) (456,968 ) (732,033 ) Net cash provided by (used in) financing activities 1,725,930 (251,393 ) (106,459 ) (a) Amounts for the year ended December 31, 2017 have not been recast to include the results of the EQM-RMP Mergers and Drop-Down Transaction.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events EQGP Buyout EQGP Unit Purchases. On January 2, 2019 and January 3, 2019, the Company closed on the acquisition of the remaining 804,140 EQGP common units that the Company did not purchase on December 31, 2018, pursuant to the Unit Purchase Agreements for an aggregate purchase price of $16.1 million . Limited Call Right. Following the Initial Unit Purchase Closing, on December 31, 2018, the Company exercised the Limited Call Right, pursuant to which, on January 10, 2019, the Company closed on the acquisition of the 11,097,287 outstanding EQGP common units not owned by the Company or its affiliates for an aggregate purchase price of $221.9 million , and EQGP became an indirect, wholly-owned subsidiary of the Company. In connection with the completion of the EQGP Buyout on January 10, 2019, certain non-employee members of the Board of Directors of the EQGP General Partner stepped down from their roles and were paid the Purchase Price for each EQGP phantom unit that they held, which was, in the aggregate, 29,829 EQGP phantom units, including accrued distributions. Termination of the EQGP Omnibus Agreement and EQGP Working Capital Facility. On January 10, 2019, EQGP's omnibus agreement with Equitrans Midstream and the EQGP Working Capital Facility were terminated. In connection with the termination of the EQGP Working Capital Facility, the Company agreed that all loans and other amounts outstanding and all other obligations of EQGP to the Company under the EQGP Working Capital Facility were deemed forgiven, satisfied, discharged and paid in full. EQM IDR Transaction On February 13, 2019, Equitrans Midstream entered into a definitive agreement and plan of merger with the EQM General Partner (the IDR Merger Agreement) and certain related parties, pursuant to which, among other things, Equitrans Midstream will exchange and cancel the IDRs and economic general partner interest in EQM that it holds, indirectly, for (a) 80 million newly-issued EQM common units and 7 million newly-issued Class B units (Class B units), both representing limited partner interests in EQM, and (b) the retention of a non-economic general partner interest in EQM (the EQM IDR Transaction). As a result of the EQM IDR Transaction, (i) EQGP Services, LLC will replace EQM Midstream Services, LLC as the general partner of EQM and (ii) the IDRs and economic general partner interest in EQM will be exchanged and canceled. The Class B units will become convertible at the holder's option in three tranches, with 2.5 million becoming convertible on April 1, 2021, 2.5 million becoming convertible on April 1, 2022, and 2 million becoming convertible on April 1, 2023 (each, a Class B unit conversion date). Until the applicable Class B unit conversion date, the Class B units will not be entitled to receive any distributions of available cash. After the applicable Class B unit conversion date, whether or not such Class B units have been converted into EQM common units, the Class B units will participate pro rata with the EQM common units in distributions of available cash. Furthermore, the Class B units will become convertible at the holder's option into EQM common units immediately before a change of control of EQM. The holders of Class B Units will vote together with the holders of EQM's common units as a single class, except that Class B Units owned by the general partner of EQM and its affiliates will be excluded from voting if EQM common units owned by such parties are excluded from voting. Holders of Class B Units will be entitled to vote as a separate class on any matter that adversely affects the rights or preferences of the Class B Units in relation to other classes of partnership interests in any material respect or as required by law. The completion of the EQM IDR Transaction is subject to certain conditions, including, among other things: (1) all required filings, consents, approvals, permits and authorizations of any governmental authority in connection with the EQM IDR Transaction having been made or obtained; (2) there being no law or injunction prohibiting the consummation of the EQM IDR Transaction; (3) subject to specified materiality standards, the accuracy of the representations and warranties of the other party; (4) compliance by the other party in all material respects with its covenants; and (5) the receipt by EQM and EQGP of certain opinions covering matters described in the partnership agreements of EQM and EQGP and in the IDR Merger Agreement with respect to the EQM IDR Transaction. The EQM IDR Transaction will be accomplished by merging a subsidiary of EQM with and into EQGP, with EQGP surviving as a wholly-owned subsidiary of EQM. The Company expects the EQM IDR Transaction to close in February 2019. After giving effect to the EQM IDR Transaction, Equitrans Gathering Holdings, EQM GP Corporation (EQM GP Corp) and Equitrans Midstream Holdings, LLC (EMH), each a subsidiary of Equitrans Midstream, will hold 89,505,616 , 89,536 and 27,650,303 of EQM's common units, respectively, representing an aggregate 56.5% limited partner interest in EQM. Additionally, Equitrans Gathering Holdings, EQM GP Corp and EMH will hold 6,153,907 , 6,155 and 839,938 of Class B units, respectively, representing an aggregate 3.4% limited partner interest in EQM. In total, the Company expects to own, directly or indirectly, a 59.9% limited partner interest in EQM, which the Company expects will consist of 117,245,455 EQM common units and 7 million Class B units. Investment in Unconsolidated Entity. See Note 7 for discussion of the MVP and MVP Southgate capital call notices and performance guarantees. Cash Dividends and EQM's Cash Distributions. See Notes 4 and 6 , respectively.

Summary of Operations and Sig_2

Summary of Operations and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation As of December 31, 2018, the EQGP General Partner was a wholly-owned subsidiary of Equitrans Gathering Holdings and controlled EQGP through its general partner interest in EQGP; therefore, the financial statements of the Company consolidate EQGP. As of December 31, 2018, the EQM General Partner was a wholly-owned subsidiary of EQGP and controlled EQM through its general partner interest in EQM; therefore, the financial statements of EQGP consolidated EQM. For each of the periods prior to the Separation presented in this Annual Report on Form 10-K, the consolidated financial statements and related notes include the assets, liabilities and results of operations of the Midstream Business that were transferred to the Company upon the closing of the Distribution and represent the predecessor for accounting purposes of Equitrans Midstream (the Predecessor). Predecessor financial information has been derived from EQT's consolidated financial statements and accounting records and reflects the historical results of operations, financial position and cash flows of the Company as if the Midstream Business had been consolidated for all periods presented. The financial statements include expense allocations for certain corporate functions historically performed by EQT, such as executive oversight, accounting, treasury, tax, legal, procurement, information technology and share-based compensation. See Note 8 . The Company believes the assumptions underlying the consolidated financial statements are reasonable; however, as organizational structure and strategic focus dictate expenses incurred, the financial statements may not include all expenses that would have been incurred had the Company existed as a standalone, publicly traded company for the entirety of the three years ended December 31, 2018. Similarly, the financial statements may not reflect the results of operations, financial position and cash flows had the Company existed as a standalone, publicly traded company. References in these financial statements to Equitrans Midstream or the Company refer collectively to Equitrans Midstream Corporation and the Predecessor as applicable for all periods presented.
Principles of Consolidation	Principles of Consolidation. The Company, for the periods presented in these consolidated financial statements prior to November 12, 2018, did not exist as a standalone, publicly-traded company holding the Midstream Business. Therefore, these consolidated financial statements are reflective of the Predecessor as applicable as described in "Basis of Presentation." Investments over which the Company can exert significant influence, but not control, are recorded under the equity method of accounting. Intercompany transactions have been eliminated for purposes of preparing these consolidated financial statements. Transactions between EQT, on the one hand, and the Company, EQGP or EQM, on the other hand, during the period prior to the Separation Date, have been identified and presented as transactions between related parties as discussed in Note 8 .
Segments	Segments. Operating segments are revenue-producing components of the enterprise for which separate financial information is produced internally and is subject to evaluation by the Company's chief operating decision maker in deciding how to allocate resources. The Company reports its operations in three segments that reflect its three lines of business of Gathering, Transmission and Water. The operating segments are evaluated based on their contribution to the Company's operating income and equity income. Transmission also includes the Company's investment in the MVP Joint Venture, which is treated as an equity investment for accounting purposes as described in Note 7 ; as a result, Transmission's portion of the MVP Joint Venture's operating results is reflected in equity income and not in Transmission's operating income. All of the Company's operating revenues, income and assets are generated or located in the United States. See Note 5 for financial information by segment.
Reclassification	Reclassification. Certain previously reported amounts have been reclassified to conform to the current year presentation.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with U.S. Generally Accepted Accounting Principles (GAAP) requires management to make estimates and assumptions that affect amounts reported in these financial statements. Actual results could differ from those estimates.
Cash Equivalents	Cash Equivalents. The Company classifies highly-liquid investments with original maturities of three months or less as cash equivalents. Interest earned on cash equivalents is recorded as a reduction to net interest expense on the statements of comprehensive income.
Accounts Receivables	Accounts Receivables. Trade and other receivables are stated at their historical carrying amount. Judgment is required to assess the ultimate realization of accounts receivable, including assessing the probability of collection and the creditworthiness of customers.
Fair Value of Financial Instruments	Fair Value of Financial Instruments. The Company categorizes assets and liabilities disclosed at fair value using a three-level fair value hierarchy based on priority of the inputs used in the valuation. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Owing to their short maturity, the carrying values of cash and cash equivalents, accounts receivable and accounts payable are assumed to approximate fair value; as such, their fair values are Level 1 fair value measurements. Interest rates on credit facility borrowings are based on prevailing market rates, so the carrying values of the credit facility borrowings approximate fair value and the fair values are Level 1 fair value measurements. As the Company's Term Loans (defined in Note 10 ) and EQM's senior notes are not actively traded, their fair values are estimated using an income approach model that applies a discount rate based on prevailing market rates for debt with similar remaining time-to-maturity and credit risk; as such, their fair values are Level 2 fair value measurements. See Note 10 . The fair value of the Preferred Interest is estimated using an income approach model that applies a discount rate based on prevailing market rates and is a Level 3 fair value measurement.
Property, Plant and Equipment	Property, Plant and Equipment. The Company's property, plant and equipment are stated at depreciated cost. Maintenance projects that do not increase the overall life of the related assets are expensed as incurred. Expenditures that extend the useful life of the asset are capitalized. The Company capitalized internal costs of $54.4 million , $46.5 million and $53.2 million in the years ended December 31, 2018, 2017 and 2016 , respectively. The Company capitalized interest, including the debt component of Allowance for Funds Used During Construction (AFUDC), of $12.6 million , $4.7 million and $9.4 million in the years ended December 31, 2018, 2017 and 2016 , respectively. The following table summarizes the Company's property, plant and equipment. December 31, 2018 2017 (Thousands) Gathering assets $ 4,387,908 $ 3,642,937 Accumulated depreciation (247,720 ) (153,791 ) Net gathering assets 4,140,188 3,489,146 Transmission and storage assets 1,785,157 1,674,080 Accumulated depreciation (286,693 ) (248,474 ) Net transmission and storage assets 1,498,464 1,425,606 Water services assets 194,465 193,825 Accumulated depreciation (26,489 ) (3,363 ) Net water services assets 167,976 190,462 Net other property, plant and equipment 61,019 5,648 Net property, plant and equipment $ 5,867,647 $ 5,110,862 Depreciation is recorded using composite rates on a straight-line basis over the estimated useful life of the asset. The average depreciation rates for the years ended December 31, 2018, 2017 and 2016 were 2.7% , 1.8% and 2.2% , respectively. The Company estimates that gathering and transmission pipelines have useful lives of 20 years to 65 years and compression equipment has useful lives of 20 years to 50 years . The Company estimates that water pipelines, pumping stations and impoundment facilities have useful lives of 10 years to 15 years . As circumstances warrant, depreciation estimates are reviewed to determine if any changes in the underlying assumptions are necessary. Equitrans, L.P., the Company's FERC-regulated subsidiary, re-evaluates depreciation rates for its regulated property, plant and equipment each time it files with the FERC for a change in transmission and storage rates.
Intangible Assets and Impairment of Long-lived Assets	Intangible Assets. Intangible assets are recorded under the acquisition method of accounting at their estimated fair values at the acquisition date, which are calculated as the present value of estimated future cash flows using a risk-adjusted discount rate. The Company did not have any intangible assets prior to the Rice Merger. At the Rice Merger Date, through pushdown accounting, the Company recorded $623.2 million of intangible assets associated with acquired customer relationships. See Note 2 . The Company's intangible assets have a useful life of 15 years and are amortized on a straight-line basis. Accumulated amortization as of December 31, 2018 and 2017 was $47.0 million and $5.5 million , respectively. Estimated annual amortization for the next five years is $41.5 million . Impairment of Long-lived Assets. Whenever events or changes in circumstances indicate that the carrying value of its long-lived assets may not be recoverable, the Company reviews its long-lived assets for impairment by first comparing the carrying value of the asset to the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the assets. If the carrying value exceeds the sum of the undiscounted cash flows, the Company estimates and recognizes an impairment loss equal to the difference between the carrying value and fair value of the assets. During the fourth quarter of 2018, a triggering event occurred as a result of the Company's annual goodwill impairment evaluation, which required the Company to perform a recoverability test on its long-lived assets. No impairment was recorded as a result of the recoverability test. No impairment of any long-lived assets was indicated or recorded during the year ended December 31, 2017 . During the year ended December 31, 2016, the Company recorded an impairment of long-lived assets of $59.7 million related to certain gathering assets. Using the income approach and Level 3 fair value measurement inputs, the gathering assets were written down to fair value. The impairment was triggered by a reduction in estimated future cash flows caused by the low commodity price environment, which reduced producer drilling activity and related throughput on the gathering assets.
Goodwill	Goodwill. Goodwill is the total consideration of an acquisition less the fair value of the identifiable, acquired net assets. As a result of the Rice Merger, Rice Midstream Holdings recorded goodwill to two reporting units within the Gathering segment. See Note 2 . Prior to the Rice Merger, the Company had no goodwill. Goodwill is evaluated for impairment at least annually and whenever events or changes in circumstance indicate that the fair value of a reporting unit is less than its carrying amount. The Company may perform either a qualitative or quantitative assessment of potential impairment. The Company's qualitative assessment of potential impairment may result in the determination that a quantitative impairment analysis is not necessary. Under this elective process, the Company assesses qualitative factors to determine whether the existence of events or circumstances leads the Company to determine that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If after assessing the totality of events or circumstances, the Company determines that it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then performing a quantitative analysis is not required. However, if the Company concludes otherwise, then it performs a quantitative impairment analysis. If the Company chooses not to perform a qualitative assessment, or if it chooses to perform a qualitative assessment but is unable to qualitatively conclude that no impairment has occurred, then the Company will perform a quantitative evaluation. In the case of a quantitative assessment, the Company estimates the fair value of the reporting unit with which the goodwill is associated and compares it to the carrying value. If the estimated fair value of a reporting unit is less than its carrying value, an impairment charge is recognized for the excess of the reporting unit's carrying value over its fair value. The two reporting units to which the Company's goodwill is recorded are (i) Rice Retained Midstream, which comprises the Ohio gathering assets acquired in the Rice Merger, and (ii) RMP PA Gas Gathering, which comprises the Pennsylvania gathering assets acquired the Rice Merger. Rice Retained Midstream and RMP PA Gas Gathering earn a substantial portion of their revenues from volumetric-based fees, which are sensitive to changes in their customers' development plans. Following the third quarter of 2018 and prior to the Separation, the Company identified impairment indicators in the form of production curtailments announced by a primary customer of the Rice Retained Midstream and RMP PA Gas Gathering reporting units that could reduce volumetric-based fee revenues of those reporting units. In estimating the fair value of its reporting units, the Company used a combination of the income approach and the market approach. The Company used the income approach's discounted cash flow method, which applies significant inputs not observable in the public market (Level 3), including estimates and assumptions related to future throughput volumes, operating costs, capital spending and changes in working capital. The Company used the market approach's comparable company method and reference transaction method. The comparable company method evaluates the value of a company using metrics of other businesses of similar size and industry. The reference transaction method evaluates the value of a company based on pricing multiples derived from similar transactions entered into by similar companies. For the year ended December 31, 2018, the Company determined that the carrying value of the RMP PA Gas Gathering reporting unit was greater than its fair value; however, the fair value of the Rice Retained Midstream reporting unit exceeded its carrying value. As a result, the Company recognized impairment of goodwill of $261.9 million , with a corresponding decrease to goodwill on the consolidated balance sheet.
Investment in Unconsolidated Entities and Noncontrolling Interests	Noncontrolling Interests. For the years ended December 31, 2018, 2017 and 2016, the Company's noncontrolling interests comprised third-party ownership interests in EQGP and EQM. For the period from November 13, 2017 through December 31, 2017 and the periods in 2018 prior to the Company's acquisition of their remaining respective noncontrolling interests as discussed herein, the Company's noncontrolling interests also included the third-party ownership interests in RMP and Gulfport Midstream's 25% ownership interest in Strike Force Midstream. Noncontrolling interests are presented as a component of equity on the consolidated balance sheets. Net income attributable to noncontrolling interests represents income allocated to third-party investors. Investment in Unconsolidated Entity. The Company reviews the carrying value of its investments in unconsolidated entities for impairment whenever events or changes in circumstances indicate that the carrying value may have declined in value. The impairment review involves comparing the investment's carrying value to its estimated fair value. If the carrying value exceeds the estimated fair value, the Company estimates and recognizes an impairment loss equal to the difference between the investment's carrying value and fair value.
Preferred Interest	Preferred Interest. EQT Energy Supply, LLC, a subsidiary of EQT (EES), generates revenue by providing services to a local distribution company. Upon EQM's acquisition of the preferred interest in EES (the Preferred Interest) in April 2015 and through October 2016, the Preferred Interest was treated as a cost method investment for accounting purposes. In October 2016, the EES operating agreement was amended to provide for mandatory redemption of the Preferred Interest at the end of the preference period, which is expected to be December 31, 2034. As a result of the amendment, EQM's investment in EES converted from a cost method investment to a note receivable effective October 1, 2016. The change did not affect the carrying value of the instrument but did affect the financial statement classification and presentation of distributions from EES. Distributions from EES received prior to the amendment were included in other income in EQM's statements of consolidated operations; distributions received after the amendment are recorded partly as a reduction to the Preferred Interest and partly as interest income, which is included in net interest expense in EQM's statements of consolidated comprehensive income.
Unamortized Debt Discount and Issuance Costs	Unamortized Debt Discount and Issuance Costs. The Company amortizes debt discounts and issuance costs over the term of the related borrowing. Costs incurred from the issuance and extension of the EQM Credit Facility (defined in Note 10 ) and the issuance of the Equitrans Midstream Credit Facility and Equitrans Midstream Term Loan Credit Facility (each as defined in Note 10 ) are presented in other assets on the consolidated balance sheets. Debt discounts and issuance costs for all other debt instruments are presented as a reduction to debt on the consolidated balance sheets.
Gas Imbalances	Gas Imbalances. Gas imbalances occur when the actual amount of gas delivered from a pipeline system or storage facility varies from the amount of gas scheduled for delivery. The Company values gas imbalances due to/from shippers and operators at current index prices. Gas imbalances are settled in-kind, subject to the terms of the FERC tariffs. As of December 31, 2018 and 2017 , gas imbalance receivables of $3.3 million and $5.2 million , respectively, were presented in other current assets, with offsetting amounts recorded to system gas, a component of property, plant and equipment, on the consolidated balance sheets. The Company classifies gas imbalances as current because they are expected to settle within one year.
Asset Retirement Obligations	Asset Retirement Obligations. The Company has asset retirement obligations related to its water system and to one of its compression stations, for which the Company recorded an associated liability and capitalized a corresponding amount to asset retirement costs. The liability relates to the expected future obligation to dismantle, reclaim and dispose of these assets and was estimated using the present value of expected future cash flows, adjusted for inflation and discounted at the Company's credit-adjusted, risk-free rate. Asset retirement obligations are recorded in regulatory and other long-term liabilities on the consolidated balance sheets.
Contingencies	Contingencies. EQM is involved in various regulatory and legal proceedings that arise in the ordinary course of business. A liability is recorded when the loss is probable and the amount of loss can be reasonably estimated. EQM considers many factors when making such assessments, including historical knowledge and matter specifics. Estimates are developed through consultation with legal counsel and analysis of the potential results. See Note 13 .
Regulatory Accounting	Regulatory Accounting. Equitrans, L.P. owns all of the Company's gathering, transmission and storage operations as well as its low-pressure gathering assets. Equitrans, L.P. is subject to FERC regulation. Through the rate-setting process, rate regulation allows Equitrans, L.P. to recover the costs of providing regulated services plus an allowed return on invested capital. Regulatory accounting allows Equitrans, L.P. to defer expenses and income to its consolidated balance sheets as regulatory assets and liabilities when it is probable that those expenses and income will be allowed in the rate-setting process for a period other than the period that they would be reflected in a non-regulated entity's statements of comprehensive income. Regulatory assets and liabilities are recognized in the Company's statements of comprehensive income in the period that the underlying expenses and income are reflected in the rates charged to shippers and operators. Equitrans, L.P. expects to continue to be subject to rate regulation that will provide for the recovery of deferred costs.
AFUDC	AFUDC. The Company capitalizes the carrying costs of financing the construction of certain long-lived, regulated assets. Such costs are amortized over the asset's estimated useful life and include interest costs (the debt component of AFUDC) and equity costs (the equity component of AFUDC). The debt component of AFUDC is recorded as a reduction to net interest expense on the statements of comprehensive income, and the equity component of AFUDC is recorded in other income on the statements of comprehensive income.
Insurance	Insurance. The Company purchases workers compensation, automobile liability and other casualty insurance. Workers compensation and automobile policies do not have a deductible or self-insured retention. The Company maintains a self-insured retention for general liability, environmental liability and other casualty lines. Under the terms of the Separation and Distribution Agreement, the Company is financially responsible for future payment of workers compensation claims incurred by EQT related to Equitrans Midstream employees prior to the Separation. The recorded reserves represent estimates of the ultimate cost of claims incurred as of the balance sheet date. The estimated liabilities are based on analysis of historical data and are not discounted. The liabilities are reviewed by management quarterly to ensure that they are appropriate. While the Company believes these estimates are reasonable based on the information available, financial results could be affected if actual trends, including the severity or frequency of claims, differ from estimates.
Share-Based Compensation	Share-Based Compensation. EQT transferred to the Company obligations related to share-based compensation awards in connection with the Separation. Outstanding awards were transferred based on a 0.80 conversion rate. Awards to employees are typically made in the form of performance-based awards, time-based restricted stock awards, time-based restricted unit awards and stock options. Awards to non-employee directors are typically made in the form of phantom unit awards (Equitrans Midstream phantom units) that vest upon grant. See Note 9 .
Pension and Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. In 2014, EQT terminated the EQT Corporation Retirement Plan for Employees (the Retirement Plan), a defined benefit pension plan. Prior to its termination, the retirees of Equitrans, L.P. participated in the Retirement Plan. On March 2, 2016, the Internal Revenue Service (IRS) issued a favorable determination letter for the termination of the Retirement Plan. On June 28, 2016, EQT purchased annuities from, and transferred the Retirement Plan assets and liabilities to, American General Life Insurance Company. In the third quarter of 2016, the Company reimbursed EQT for its proportionate share of the funding related to the retirees of Equitrans, L.P. The settlement charge is expected to be recoverable in FERC-approved rates and, thus, was recorded as a regulatory asset that will be amortized for rate recovery purposes over a period of 16 years . Upon Separation, EQT transferred to the Company the post-retirement benefits liability and accumulated other comprehensive income balance associated with the Retirement Plan. The Company recognizes expense for on-going post-retirement benefits other than pension, a portion of which is subject to recovery in the approved rates of Equitrans, L.P.'s rate-regulated business. See Note 14 . The Company presents the associated pension and other post-retirement benefits liability adjustment, net of tax, as a reclassification from accumulated other comprehensive income on the statements of consolidated comprehensive income and consolidated equity and on the consolidated balance sheets. The accumulated other comprehensive income reclassification relates to the net actuarial loss and net prior service costs related to the Company's Retirement Plan.
Income Taxes	Income Taxes. Beginning on the Separation Date and forward, the provision for income taxes was determined using the asset and liability approach of accounting for income taxes. Under this approach, the provision for income taxes represents income taxes paid or payable (or received or receivable) for the current year plus the change in deferred taxes during the year. In all periods prior to the Separation Date, the Company's operations were included in the income tax filings of EQT. The provision for income taxes in the Company's consolidated statements of comprehensive income was determined in the same manner described above, but on a separate return methodology as if the Company was a standalone taxpayer filing hypothetical income tax returns where applicable. Any additional accrued tax liability or refund arising as a result of this approach was assumed to be settled with EQT on the Separation Date as a component of parent net investment. The Company's operations have historically been included in the income tax filings of EQT. The provision for income taxes reflected in the Company's statements of comprehensive income for periods prior to the Separation Date is based on a separate return methodology using the asset and liability approach of accounting for income taxes. Under this approach, the provision for income taxes represents income taxes paid or payable (or received or receivable) for the current year plus the change in deferred taxes during the year, which is calculated as if the Company was a standalone taxpayer filing hypothetical income tax returns where applicable. Any accrued current tax liability or refund arising from this approach was presented in accounts payable as an amount due to related party on the consolidated balance sheets and was settled with EQT as a component of parent's net investment on an annual basis. Deferred taxes represent the future tax consequences of differences between the financial and tax bases of the Company's assets and liabilities. Deferred tax balances are adjusted for changes in tax rates and tax laws when enacted. Deferred tax assets are reflected on the consolidated balance sheets for net operating losses, credits or other attributes transferred to or generated by the Company. Any difference between the attributes transferred to the Company and the attributes generated on a separate return basis were adjusted as a component of parent net investment. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not (greater than 50%) that a tax benefit will not be realized. In evaluating the need for a valuation allowance, management considers all potential sources of taxable income, including income available in carry-back periods, future reversals of taxable temporary differences, projections of taxable income and income from tax planning strategies, as well as all available positive and negative evidence. Positive evidence includes factors such as a history of profitable operations, projections of future profitability within the carry-forward period, including from tax planning strategies, and experience. No significant negative evidence has been noted. Deferred tax assets for which no valuation allowance is recorded may not be realized and changes in facts and circumstances may result in the establishment of a valuation allowance. Existing valuation allowances are re-examined under the same standards of positive and negative evidence that apply to valuation allowance establishment. If it is determined that it is more likely than not that a deferred tax asset for which a valuation is recorded will be realized, all or a portion of the valuation allowance may be released. Deferred tax assets and liabilities are also re-measured to reflect changes in underlying tax rates from law changes. Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more likely than not threshold; otherwise, the tax benefit is recorded when the tax position has been effectively settled, either because the statute of limitations has expired or the appropriate taxing authority has completed its examination. Interest and penalties related to uncertain tax positions are recognized as part of the provision for income taxes and are accrued beginning in the period that such interest and penalties would be applicable under relevant tax law until such time that the related tax benefits are recognized. The Company has not identified any uncertain tax positions as of December 31, 2018 , 2017 and 2016 . See Note 11 .
Earnings Per Share (EPS)	Earnings Per Share (EPS). Basic EPS is computed by dividing net income attributable to Equitrans Midstream by the weighted average number of shares of Equitrans Midstream common stock outstanding during the period without considering any dilutive items. Diluted EPS is computed by dividing net income attributable to Equitrans Midstream by the weighted average number of shares of Equitrans Midstream common stock and potentially dilutive securities, net of shares assumed to be repurchased using the treasury stock method. Purchases of treasury stock are calculated using the average share price of Equitrans Midstream common stock during the period. Potentially dilutive securities arise from the assumed conversion of outstanding stock options and other share-based awards. For the years ended December 31, 2018 and 2016, the Company's computation of EPS included potentially dilutive securities related to stock options and awards of 601,622 . For the year ended December 31, 2017, because the Company generated a net loss, the Company's computation of EPS excluded potentially dilutive securities; as such, basic and diluted weighted average common stock outstanding were the same for the year ended December 31, 2017. See Note 9 for information on the Company's stock options and awards. The Company grants Equitrans Midstream phantom units to certain non-employee directors that will be paid in Equitrans Midstream common stock upon the director's termination of service on the Company's Board of Directors (the Board). As there are no remaining service, performance or market conditions related to these awards, 161,696 Equitrans Midstream phantom units were included in the computation of basic and diluted weighted average common shares outstanding for the years ended December 31, 2018, 2017 and 2016. See Note 9 for information on Equitrans Midstream phantom units. For periods prior to the Separation Date, EPS shown on the statements of consolidated comprehensive income and in Note 15 was calculated based on the shares of Equitrans Midstream common stock distributed in connection with the Separation and Distribution and is considered pro forma in nature. Prior to the Separation Date, the Company did not have any issued or outstanding common stock (other than shares owned by EQT).
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2014-09, Revenue from Contracts with Customers . The standard requires entities to recognize revenue in a manner that depicts the transfer of goods or services to customers at an amount that reflects the consideration the entity expects in exchange for those goods or services. The Company adopted this standard on January 1, 2018 using the modified retrospective method of adoption. Adoption of the standard did not require an adjustment to the opening balance of equity. The Company has implemented processes and controls to review new contracts for appropriate accounting treatment in the context of the standard and to generate disclosures required under the standard. For the disclosures required by the standard, see Note 3 . In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments – Overall: Recognition and Measurement of Financial Assets and Financial Liabilities . The standard primarily affects the accounting for equity investments, the accounting for financial liabilities measured under the fair value option and the presentation and disclosure of financial instruments and eliminates the cost method of accounting for equity investments. The Company adopted this standard in the first quarter of 2018 with no significant effect on its financial statements or related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases . The standard requires entities to record assets and obligations for contracts currently recognized as operating leases. In July 2018, the FASB targeted improvements to ASU 2016-02 through its issuance of ASU No. 2018-11. This update provides entities with an optional transition method, which permits an entity to initially apply the standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The standard also allows for election of transition practical expedients. The Company adopted the standards on January 1, 2019 using the optional transition method of adoption. Adoption of the standards did not require an adjustment to the opening balance of equity. For leases with commencement dates prior to the effective date, the Company elected to apply the package of practical expedients that state (i) an entity need not reassess whether any expired or existing contracts are or contain leases, (ii) an entity need not reassess the lease classification for any expired or existing leases, and (iii) an entity need not reassess initial direct costs for any existing leases. The Company elected not to use hindsight in determining the lease term. Additionally, the Company elected not to assess whether existing or expired land easements that were not previously accounted for as leases under Topic 840 are or contain a lease under Topic 840. The quantitative impacts of the standards are dependent on the leases in force at the time of reporting. As a result, the evaluation of the effect of the standards on the results of operations and liquidity will extend over future periods. However, the Company does not expect the standards to have a significant effect on its results of operations or liquidity in 2019. On January 1, 2019, the Company recognized a right-of-use asset and corresponding lease liability of approximately $50 million on its consolidated balance sheet related to its facilities and compressor operating leases. The Company has no capital leases. Additional disclosures will be required to describe the nature, maturity and amount of the Company's lease liabilities, including the significant assumptions and judgments required to value its lease liabilities, and the accounting policy elections taken. The Company is using a lease accounting system to document its current population of contracts classified as leases, which will be updated as the Company's lease population changes. The Company is implementing processes and controls to review new lease contracts for appropriate accounting treatment in the context of the standards and to generate disclosures required under the standards, which the Company expects to disclose in its Quarterly Report on Form 10-Q for the first quarter of 2019. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments . The standard amends guidance on reporting credit losses on assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, this standard eliminates the probable initial recognition threshold and, in its place, requires entities to recognize the current estimate of all expected credit losses. The amendments affect loans, debt securities, trade receivables, net investments in leases, off balance sheet credit exposures, reinsurance receivables and any other financial assets not excluded from the scope of the standard that have the contractual right to receive cash. The standard will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. The Company is currently evaluating the effect this standard will have on its financial statements and related disclosures. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations: Clarifying the Definition of a Business . The standard provides guidance on evaluating whether a transaction should be accounted for as an acquisition (or disposal) of assets or a business. The Company adopted the standard in the first quarter of 2018 with no significant effect on its financial statements or related disclosures. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test of Goodwill Impairment . The standard simplifies the quantitative goodwill impairment test requirements by eliminating the requirement to calculate the implied fair value of goodwill. Instead, an entity would record an impairment charge based on the excess of a reporting unit's carrying value over its fair value. The Company adopted this standard in the first quarter of 2018 with no significant effect on its financial statements or related disclosures. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation: Scope of Modification Accounting . The standard provides guidance on evaluating whether a change to the terms or conditions of a share-based award requires modification accounting. The Company adopted the standard in the first quarter of 2018 with no significant effect on its financial statements or related disclosures. The standard will be applied prospectively to awards modified on or after the adoption date. In February 2018, the FASB issued ASU 2018-02, Income Statement, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , which allows for a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Reform Legislation (described in Note 11) and will improve the usefulness of information reported to financial statement users. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The Company plans to adopt this standard in 2019 but does not expect the adoption of this standard to have a material effect on its financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement, Changes to the Disclosure Requirements for Fair Value Measurement , which makes a number of changes to the hierarchy associated with Level 1, 2 and 3 fair value measurements and the related disclosure requirements. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the effect this standard will have on its financial statements and related disclosures but does not expect the adoption of this standard to have a material effect on its financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-15, Intangibles – Goodwill and Other: Internal-Use Software , which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company early-adopted the standard using the prospective method of adoption on January 1, 2019. The Company does not expect the adoption of this standard to have a significant effect on its results of operations, liquidity or financial position in 2019. Additional disclosures will be required to describe the nature of the Company's hosting arrangements that are service contracts and to report the capitalized implementation costs as a separate major class of depreciable assets.
Revenue from Contracts with Customers	Revenue from Contracts with Customers As discussed in Note 1 , the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers , on January 1, 2018 using the modified retrospective method of adoption. The Company applied the standard to all open contracts as of the date of initial application. Adoption of the standard did not require an adjustment to the opening balance of equity and did not materially change the amount or timing of the Company's revenues. For the years ended December 31, 2018, 2017 and 2016 , all revenues recognized on the Company's statements of comprehensive income are from contracts with customers. As of December 31, 2018 and 2017 , all receivables recorded on the Company's consolidated balance sheets represent performance obligations that have been satisfied and for which an unconditional right to consideration exists. Gathering, Transmission and Storage Service Contracts The Company provides gathering, transmission and storage services in two manners: firm service and interruptible service. Firm service is provided under firm contracts, which are contracts for gathering, transmission or storage services that generally obligate the customer to pay a fixed, monthly charge to reserve an agreed upon amount of pipeline or storage capacity regardless of the capacity used by the customer during each month. Volumetric-based fees can also be charged under firm contracts for each firm volume transported, gathered or stored as well as for volumes transported, gathered or stored in excess of the firm contracted volume. Interruptible service contracts include volumetric-based fees, which are charges for the volume of gas gathered, transported or stored and generally do not guarantee access to the pipeline or storage facility. These contracts can be short- or long-term. Firm and interruptible contracts are billed at the end of each calendar month, with payment typically due within 21 days. Under a firm contract, the Company has a stand-ready obligation to provide the service over the life of the contract. The performance obligation for firm reservation fee revenue is satisfied over time as the pipeline capacity is made available to the customer. As such, the Company recognizes firm reservation fee revenue evenly over the contract period using a time-elapsed output method to measure progress. The performance obligation for volumetric-based fee revenue is generally satisfied upon the Company's monthly billing to the customer for volumes gathered, transported or stored during the month. The amount billed corresponds directly to the value of the Company's performance to date as the customer obtains value as each volume is gathered, transported or stored. Certain of the Company's gas gathering agreements are structured with minimum volume commitments (MVCs), which specify minimum quantities for which a customer will be charged regardless of quantities gathered under the contract. Revenue is recognized for MVCs when the performance obligation has been met, which is the earlier of when the gas is gathered or when it is remote that the producer will be able to meet its MVC. Water Service Contracts Water service revenues represent fees charged by the Company for the delivery of fresh water to a customer at a specified delivery point and for the collection and recycling or disposal of flowback and produced water. All of the Company's water service revenues are generated under variable price per volume contracts. For fresh water service contracts, the only performance obligation in each contract is for the Company to provide water (usually a minimum daily volume of water) to the customer at a designated delivery point. For flowback and produced water, the performance obligation is collection and disposition of the water, which typically occur within the same day. Water service contracts are billed on a monthly basis, with payment typically due within 21 days. Based on total projected contractual revenues, including projected contractual revenues from future capacity expected from expansion projects that are not yet fully constructed for which the Company has executed firm contracts, the Company's firm gathering contracts and firm transmission and storage contracts had weighted average remaining terms of approximately 11 years and 15 years, respectively, as of December 31, 2018 .

Summary of Operations and Sig_3

Summary of Operations and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of property, plant and equipment	The following table summarizes the Company's property, plant and equipment. December 31, 2018 2017 (Thousands) Gathering assets $ 4,387,908 $ 3,642,937 Accumulated depreciation (247,720 ) (153,791 ) Net gathering assets 4,140,188 3,489,146 Transmission and storage assets 1,785,157 1,674,080 Accumulated depreciation (286,693 ) (248,474 ) Net transmission and storage assets 1,498,464 1,425,606 Water services assets 194,465 193,825 Accumulated depreciation (26,489 ) (3,363 ) Net water services assets 167,976 190,462 Net other property, plant and equipment 61,019 5,648 Net property, plant and equipment $ 5,867,647 $ 5,110,862
Schedule of asset retirement obligations	The following table presents a reconciliation of the beginning and ending carrying amounts of the Company's asset retirement obligations. December 31, 2018 2017 (Thousands) Asset retirement obligation at beginning of period $ 9,321 $ — Liabilities assumed at Rice Merger — 9,286 Liabilities incurred 231 — Revisions to estimated liabilities (a) 1,928 — Accretion expense 455 35 Asset retirement obligation at end of period $ 11,935 $ 9,321 (a) Revisions to estimated liabilities reflect changes in retirement cost assumptions and to the estimated timing of liability settlement.
Schedule of regulatory assets	The following table summarizes Equitrans, L.P.'s regulatory assets and liabilities that are included in other assets and regulatory and other long-term liabilities, respectively, in the Company's consolidated balance sheets. December 31, 2018 2017 (Thousands) Regulatory assets: Deferred taxes (a) $ 22,252 $ 18,786 Other recoverable costs (b) 4,312 6,165 Total regulatory assets $ 26,564 $ 24,951 Regulatory liabilities: Deferred taxes (a) $ 10,920 $ 11,318 On-going post-retirement benefits other than pension (c) 10,132 7,724 Other reimbursable costs (328 ) 860 Total regulatory liabilities $ 20,724 $ 19,902 (a) The regulatory asset from deferred taxes is primarily related to a historical deferred income tax position and taxes on the equity component of AFUDC. The regulatory liability from deferred taxes relates to the revaluation of a historical difference between the regulatory and tax bases of regulated property, plant and equipment. Equitrans, L.P. expects to recover the amortization of the deferred tax positions ratably over the depreciable lives of the underlying assets. Equitrans, L.P. expects to recover the taxes on the equity component of AFUDC through future rates over the depreciable lives of the underlying long-lived assets. (b) The regulatory asset from other recoverable costs is primarily related to the costs associated with the Retirement Plan (defined below). (c) Equitrans, L.P. defers expenses for on-going post-retirement benefits other than pensions, which are subject to recovery in approved rates. The regulatory liability reflects lower cumulative actuarial expenses than the amounts recovered through rates.
Schedule of regulatory liabilities	The following table summarizes Equitrans, L.P.'s regulatory assets and liabilities that are included in other assets and regulatory and other long-term liabilities, respectively, in the Company's consolidated balance sheets. December 31, 2018 2017 (Thousands) Regulatory assets: Deferred taxes (a) $ 22,252 $ 18,786 Other recoverable costs (b) 4,312 6,165 Total regulatory assets $ 26,564 $ 24,951 Regulatory liabilities: Deferred taxes (a) $ 10,920 $ 11,318 On-going post-retirement benefits other than pension (c) 10,132 7,724 Other reimbursable costs (328 ) 860 Total regulatory liabilities $ 20,724 $ 19,902 (a) The regulatory asset from deferred taxes is primarily related to a historical deferred income tax position and taxes on the equity component of AFUDC. The regulatory liability from deferred taxes relates to the revaluation of a historical difference between the regulatory and tax bases of regulated property, plant and equipment. Equitrans, L.P. expects to recover the amortization of the deferred tax positions ratably over the depreciable lives of the underlying assets. Equitrans, L.P. expects to recover the taxes on the equity component of AFUDC through future rates over the depreciable lives of the underlying long-lived assets. (b) The regulatory asset from other recoverable costs is primarily related to the costs associated with the Retirement Plan (defined below). (c) Equitrans, L.P. defers expenses for on-going post-retirement benefits other than pensions, which are subject to recovery in approved rates. The regulatory liability reflects lower cumulative actuarial expenses than the amounts recovered through rates.
Schedule of regulated operating revenues, expenses, property, plant and equipment	The following tables present Equitrans, L.P.'s regulated operating revenues and operating expenses and property, plant and equipment included in the Company's statements of comprehensive income and consolidated balance sheets, respectively. Years Ended December 31, 2018 2017 2016 (Thousands) Operating revenues $ 393,911 $ 383,309 $ 343,978 Operating expenses 140,832 143,614 114,978 December 31, 2018 2017 (Thousands) Property, plant and equipment $ 1,900,411 $ 1,787,656 Accumulated depreciation (317,988 ) (278,756 ) Net property, plant and equipment $ 1,582,423 $ 1,508,900
Schedule of non-cash cash flow activity	The following summarizes cash paid during the period for interest, net of amount capitalized and non-cash activity included on the consolidated statements of cash flow. Years Ended December 31, 2018 2017 2016 (Thousands) Cash paid during the period for: Interest, net of amount capitalized $ 54,089 $ 43,797 $ 13,902 Non-cash activity during the period for: Acquisition of Rice Midstream Holdings LLC $ — $ 3,846,240 $ — Settlement of separation and other transaction costs with EQT 133,286 — — Net settlement of current income taxes payable with EQT 54,033 115,819 536,871 Elimination of net current and deferred tax liabilities — — 1,945 Separation-related adjustments 228,357 — — Revision to estimated asset retirement obligations 1,928 — —

Rice Energy Merger (Tables)

Rice Energy Merger (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of summary of preliminary purchase price and allocation of fair value of assets and liabilities	$1,384.9 million to two reporting units within the Gathering segment. In connection with the Separation, EQT transferred to the Company a deferred tax liability assumed in the Rice Merger and a corresponding increase to goodwill of $137.0 million . During the fourth quarter of 2018, the Rice Merger purchase price accounting was finalized and, as a result, the Company recorded a reduction of $20.7 million to goodwill and a corresponding increase of $0.9 million to accounts payable and decrease of $21.6 million to deferred tax liability. The following table summarizes the final purchase price allocation of the fair value of the assets and liabilities of Rice Midstream Holdings as of the Rice Merger Date. These values were recorded by Rice Midstream Holdings through pushdown accounting from EQT. Rice Merger Purchase Price Allocation and Goodwill (Thousands) Enterprise value (a) $ 3,846,240 Fair value of assets acquired and liabilities assumed: Current assets 141,410 Property, plant and equipment 2,265,924 Intangible assets 623,200 Other assets 118 Current liabilities (107,101 ) RMP Credit Facility (266,000 ) Due to EQT (b) (187,742 ) Deferred income taxes (115,456 ) Other long-term liabilities (9,323 ) Total fair value of assets acquired and liabilities assumed 2,345,030 Goodwill (c) 1,501,210 Impairment of goodwill (d) 261,941 Goodwill as of December 31, 2018 $ 1,239,269 (a) Includes the fair value of noncontrolling interests assumed of $1.5 billion and $0.2 billion for RMP and Strike Force Midstream, respectively. (b) At the time of the Rice Merger, EQT repaid $187.5 million of outstanding principal and $0.2 million in accrued interest under Rice Midstream Holdings' revolving credit facility. Following repayment, EQT terminated the Rice Midstream Holdings revolving credit facility agreement. As of December 31, 2017, the $187.7 million is included in accounts payable on the Company's consolidated balance sheet. The Company reimbursed EQT for this amount in 2018. (c) Reflected the value of perceived growth opportunities, synergies and operating leverage anticipated through the acquisition and ownership of the acquired gathering assets as of November 13, 2017. (d) See Note 1 for discussion of the Company's evaluation and recognition of the impairment of goodwill for the year ended December 31, 2018.
Schedule of post-acquisition operating results	Subsequent to the completion of the Rice Merger, Rice Midstream Holdings contributed the following to the Company's consolidated operating results for the period from November 13, 2017 through December 31, 2017. November 13, 2017 through December 31, 2017 (Thousands) Operating revenues $ 14,881 Operating income attributable to Equitrans Midstream 69,036 Net income attributable to noncontrolling interests 16,644 Net income attributable to Equitrans Midstream 21,814
Schedule of unaudited pro-forma information	The following unaudited pro forma financial information presents the Company's results as though the Rice Merger had been completed at January 1, 2016. The pro forma financial information has been included for comparative purposes and is not necessarily indicative of the results that might have actually occurred had the Rice Merger taken place on January 1, 2016; furthermore, the financial information is not intended to be a projection of future results. Years Ended December 31, 2017 2016 (Thousands) Pro forma operating revenues $ 1,264,704 $ 997,829 Pro forma net income 549,567 440,735 Pro forma net income attributable to noncontrolling interests 445,576 376,284 Pro forma net income attributable to Equitrans Midstream 103,991 64,451

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregated Revenue Information, by Business Segment	The tables below provide disaggregated revenue information by business segment. Year Ended December 31, 2018 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 447,360 $ 356,725 $ — $ 804,085 Volumetric-based fee revenues 549,710 30,076 — 579,786 Water service revenues — — 111,227 111,227 Total operating revenues $ 997,070 $ 386,801 $ 111,227 $ 1,495,098 Year Ended December 31, 2017 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 407,355 $ 348,193 $ — $ 755,548 Volumetric-based fee revenues 102,612 23,793 — 126,405 Water service revenues — — 13,605 13,605 Total operating revenues $ 509,967 $ 371,986 $ 13,605 $ 895,558 Year Ended December 31, 2016 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 339,237 $ 277,816 $ — $ 617,053 Volumetric-based fee revenues 58,257 56,962 — 115,219 Water service revenues — — — — Total operating revenues $ 397,494 $ 334,778 $ — $ 732,272
Summary of Remaining Performance Obligations	The following table summarizes the transaction price allocated to the Company's remaining performance obligations under all contracts with firm reservation fees and MVCs as of December 31, 2018 . 2019 2020 2021 2022 2023 Thereafter Total (Thousands) Gathering firm reservation fees $ 476,709 $ 552,636 $ 562,635 $ 562,635 $ 562,635 $ 2,273,123 $ 4,990,373 Gathering revenues supported by MVCs 65,700 71,370 71,175 71,175 71,175 65,700 416,295 Transmission firm reservation fees 351,028 343,984 340,218 335,137 295,243 2,178,736 3,844,346 Total $ 893,437 $ 967,990 $ 974,028 $ 968,947 $ 929,053 $ 4,517,559 $ 9,251,014

Financial Information by Busi_2

Financial Information by Business Segment (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Operating Income and Reconciliation to Net Income	Years Ended December 31, 2018 2017 2016 (Thousands) Revenues from external customers (including related parties): Gathering $ 997,070 $ 509,967 $ 397,494 Transmission 386,801 371,986 334,778 Water 111,227 13,605 — Total operating revenues $ 1,495,098 $ 895,558 $ 732,272 Operating income (loss): Gathering (a) $ 423,407 $ 369,093 $ 289,643 Transmission 265,579 247,467 238,213 Water 37,667 4,145 — Other (b) (83,569 ) (77,655 ) (62,790 ) Total operating income $ 643,084 $ 543,050 $ 465,066 Reconciliation of operating income to net income: Equity income (c) 61,778 22,171 9,898 Other income 5,011 4,439 27,113 Net interest expense 115,454 34,801 16,761 Income tax expense 83,142 212,402 98,243 Net income $ 511,277 $ 322,457 $ 387,073 (a) Impairment of goodwill of $261.9 million was included in Gathering's operating income for 2018. See Note 1. (b) Other operating loss includes selling, general and administrative expense, separation and other transaction costs and depreciation that are not allocated to the business segments. (c) Equity income is included in the Transmission segment.
Schedule of Segment Assets	December 31, 2018 2017 (Thousands) Segment assets: Gathering $ 6,011,654 $ 5,656,094 Transmission (a) 3,066,659 1,947,566 Water 237,602 208,273 Total operating segments 9,315,915 7,811,933 Headquarters, including cash 1,207,920 516,863 Total assets $ 10,523,835 $ 8,328,796 (a) The equity investment in the MVP Joint Venture is included in the Transmission segment.
Schedule of Depreciation and Amortization and Expenditures for Segment Assets	Years Ended December 31, 2018 2017 2016 (Thousands) Depreciation: Gathering $ 98,678 $ 44,957 $ 30,422 Transmission 49,723 58,689 32,269 Water 23,513 3,515 — Other (a) 3,907 (10,487 ) — Total $ 175,821 $ 96,674 $ 62,691 Expenditures for segment assets: Gathering $ 717,251 $ 254,522 $ 295,315 Transmission 114,450 111,102 292,049 Water 23,537 6,233 — Other 29,336 — — Total (b) $ 884,574 $ 371,857 $ 587,364 (a) Depreciation within the Transmission segment for the year ended December 31, 2017 includes a non-cash charge of $10.5 million related to the revaluation of differences between the regulatory and tax bases in Equitrans, L.P.'s regulated property, plant and equipment. For purposes of the Company's consolidated reporting, the $10.5 million is reported in income tax expense with a corresponding reduction to depreciation. (b) The Company accrues capital expenditures when the capital work has been completed but the associated bills have not been paid. Accrued capital expenditures are excluded from the statements of consolidated cash flows until they are paid. Accrued capital expenditures were approximately $109.3 million , $90.7 million , $26.7 million and $24.1 million at December 31, 2018 , 2017 , 2016 and 2015 , respectively. At the Rice Merger Date, the Company assumed $72.3 million of Rice Midstream Holdings accrued capital expenditures.

Investments in Consolidated, _2

Investments in Consolidated, Non-Wholly-Owed Entities (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Net Changes in Ownership of EQGP and EQM	The following table summarizes the net changes in the Company's parent net investment from changes in the Company's ownership interests in EQGP or EQM for the year ended December 31, 2018 . EQGP and EQM had no equity transactions in 2017, and, as such, there were no changes in the Company's net ownership of EQGP or EQM. During the year ended December 31, 2016, as a result of EQM common units issued under the $750 Million ATM Program and through vestings of long-term incentive plan awards, the Company recorded a gain to parent net investment of approximately $24 million , an increase to deferred tax liability of approximately $16 million and a decrease in noncontrolling interest in consolidated subsidiaries of approximately $40 million . Year Ended December 31, 2018 (Millions) Net changes in parent net investment Drop-Down Transaction $ 16 RMP IDR Transaction (35 ) EQM-RMP Mergers (140 ) Net decrease in parent net investment (159 ) Net decrease in deferred tax liability 56 Net increase in noncontrolling interest in consolidated subsidiaries $ 215

Investments in Unconsolidated_2

Investments in Unconsolidated Entity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Unaudited Condensed Financial Statements for the Investment in Unconsolidated Equity	The following tables summarize the audited financial statements of the MVP Joint Venture. Consolidated Balance Sheets December 31, 2018 2017 (Thousands) Current assets $ 687,657 $ 330,271 Noncurrent assets 3,223,220 747,728 Total assets $ 3,910,877 $ 1,077,999 Current liabilities $ 617,355 $ 65,811 Equity 3,293,522 1,012,188 Total liabilities and equity $ 3,910,877 $ 1,077,999 Statements of Consolidated Operations Years Ended December 31, 2018 2017 2016 (Thousands) AFUDC – equity $ 91,056 $ 32,054 $ 16,315 Net interest income 44,786 16,674 5,206 Net income $ 135,842 $ 48,728 $ 21,521

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Schedule of related party transactions	The following table summarizes the Company's related party transactions. Years Ended December 31, 2018 2017 2016 (Thousands) Operating revenues $ 1,111,289 $ 665,939 $ 551,353 Operating and maintenance expense (a) 49,778 40,601 34,179 Selling, general and administrative expense (a) 85,081 75,610 70,387 Separation and other transaction costs (a) (b) 53,272 85,124 — Equity income 61,778 22,171 9,898 Other income from the Preferred Interest — — 8,293 Interest income from the Preferred Interest 6,578 6,818 1,740 Net interest expense (b) 5 (2,120 ) 3 Net (payments on) proceeds from EQGP's working capital loan with EQT (168 ) 84 18 Capital contributions to the MVP Joint Venture (913,195 ) (159,550 ) (98,399 ) Principal payments received on the Preferred Interest 4,406 4,166 1,024 Net (distributions to) contributions from EQT (701,901 ) (893,682 ) 740,797 (a) Reimbursements to EQT may not necessarily reflect the actual expenses that the Company would have incurred on a standalone basis. The Company is unable to estimate what those expenses would be on a standalone basis. (b) For the years ended December 31, 2018 and 2017 , separation and other transaction costs included charges related to the Rice Merger from EQT of $13.7 million and $85.1 million , respectively. In addition, in 2017, the Company recorded $ 2.9 million in interest expense related to EQT's financing of the Rice Merger that was allocated to the Company from EQT. The basis for allocation of both the Rice Merger transaction costs and interest expense was the relative fair value of Rice Midstream Holdings' net assets acquired by EQT and distributed to the Company in the Rice Merger. See Note 2 . For the year ended December 31, 2018, separation and transaction costs included charges related to the Drop-Down Transaction, the EQM-RMP Mergers and the Separation from EQT of $39.6 million . The basis for allocated separation costs was 50% of such costs incurred by EQT. The following table summarizes the Company's related party receivables and payables. December 31, 2018 2017 (Thousands) Accounts receivable – related parties $ 175,869 $ 158,720 Investment in unconsolidated entity 1,510,289 460,546 Preferred Interest 114,720 119,127 Accounts payable – related parties 34,071 363,058 Capital contribution payable to the MVP Joint Venture 169,202 105,734

Share-based Compensation Plans

Share-based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation Expense	The following table summarizes the components of share-based compensation expense for the year ended December 31, 2018. Year Ended December 31, 2018 (Thousands) 2016 EQT Incentive Performance Share Unit Program $ 956 2017 EQT Incentive Performance Share Unit Program 1,642 2018 EQT Incentive Performance Share Unit Program 906 2017 EQT Value Driver Performance Share Unit Award Program 255 2018 EQT Value Driver Performance Share Unit Award Program 2,890 Restricted stock awards 1,048 Non-qualified stock options 201 Other programs, including non-employee director awards 2,678 Total share-based compensation expense $ 10,576
Schedule of Details of Award Types	The following table provides detailed information on each award: EQT VDPSU Program Settled In Accounting Treatment Fair Value per Unit (a) Vested/ Payment Date Cash Paid (Millions) Unvested/ Expected Payment Date Awards Outstanding (Including Accrued Dividends) as of December 31, 2018 (b) 2017 Cash Liability $ 20.02 N/A N/A First Quarter of 2019 170,966 2018 Cash Liability $ 20.02 N/A N/A First Tranche First Quarter of 2019 205,420 N/A N/A N/A Second Tranche First Quarter of 2020 205,781 (a) The fair value per unit is calculated as a weighted average of the Company's and EQT's respective common stock prices on the measurement date. (b) The 2017 and 2018 EQT VDPSU Programs include 94,488 and 194,460 awards, respectively, for EQT employees that will be settled by the Company under the Employee Matters Agreement. The following table provides detailed information on each award: Incentive PSU Program Settled In Accounting Treatment Fair Value (a) Risk Free Rate Vested/ Payment Date Awards Paid Value (Millions) Unvested/ Expected Payment Date (b) Awards Outstanding as of December 31, 2018 (c) 2016 Stock Equity $ 109.30 1.31 % N/A N/A N/A First Quarter of 2019 307,553 2017 Stock Equity $ 120.60 1.47 % N/A N/A N/A First Quarter of 2020 35,728 2017 Cash Liability $ 59.90 2.61 % N/A N/A N/A First Quarter of 2020 84,014 2018 Stock Equity $ 76.53 1.97 % N/A N/A N/A First Quarter of 2021 85,872 2018 Cash Liability $ 33.87 2.46 % N/A N/A N/A First Quarter of 2021 100,435 (a) Grant date fair value was determined using a Monte Carlo simulation for equity awards. Fair value was determined using a Monte Carlo simulation as of the measurement date for liability awards. For unvested Incentive PSU Programs, the grant date fair value for equity awards and the measurement date fair value for liability awards is as of December 31, 2018 . The Company recorded compensation expense as of December 31, 2018 using the grant date fair value for equity awards and the measurement date fair value for liability awards, each computed for the outcome that management estimates to be most probable. (b) Vesting will occur upon payment following the expiration of the performance period, subject to continued service through such date. (c) Represents the number of outstanding units as of December 31, 2018 , adjusted for forfeitures. The 2016, 2017 and 2018 Incentive PSU Programs to be settled in stock include 203,238 , 30,112 , and 58,160 shares, respectively, for EQT employees that will be settled by the Company under the Employee Matters Agreement. The 2017 and 2018 Incentive PSU Programs to be settled in cash include 46,297 and 54,643 shares, respectively, for EQT employees that will be settled by the Company under the Employee Matters Agreement.
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	The following table sets forth the total compensation costs capitalized related to the Incentive PSU Programs. Year Ended December 31, 2018 (Thousands) 2016 Incentive PSU Program $ 80.8 2017 Incentive PSU Program (liability only) 1,046.8 2018 Incentive PSU Program (liability only) 304.9 The following table sets forth the total compensation costs capitalized related to the VDPSU Programs. Year Ended December 31, 2018 (Thousands) 2017 EQT VDPSU Program $ 955.4 2018 EQT VDPSU Program 1,903.2
Non-Qualified Stock Options, Assumptions Used to Value Share-based Compensation	Refer to the table below for assumptions used in the Black-Scholes option-pricing model. Risk-free rates for periods within the contractual life of the option are based on the U.S. Treasury yield curve in effect at the date of grant. Dividend yields are based on the dividend yield of EQT's common stock at the time of grant. Expected volatilities are based on historical volatility of EQT's common stock. Expected term represents the period that options granted are expected to be outstanding based on historical option exercise experience. Years Ended December 31, 2018 2017 2016 Risk-free rate 2.25 % 1.95 % 1.67 % Dividend yield 0.20 % 0.18 % 0.16 % Volatility factor 26.46 % 27.45 % 28.59 % Expected term 5 Years 5 Years 5 Years Options transferred in connection with the Separation 57,440 32,560 105,600 Weighted average grant date fair value $ 8.55 $ 9.89 $ 8.53 Total intrinsic value of options exercised (Millions) $ — $ — $ — The following table summarizes the weighted-average assumptions used in the Monte Carlo simulation to estimate fair value: Years Ended December 31, 2018 2017 2016 Accounting Treatment Liability (a) Equity Liability (a) Equity Equity Risk-free rate 2.46 % 1.97 % 2.61 % 1.47 % 1.31 % Dividend yield (b) N/A N/A N/A N/A N/A Volatility factor 35.70 % 32.60 % 41.17 % 32.30 % 28.43 % Expected term 2 Years 3 Years 1 Year 3 Years 3 Years (a) Information shown for the valuation of the liability plan is as of measurement date. (b) Dividends paid from the beginning of the performance period will be cumulatively added as additional shares of common stock.
Schedule of Restricted Stock Awards Activity	A summary of restricted stock equity award activity as of December 31, 2018 , and changes during the year then ended, is presented below. Non-vested Shares (a) Weighted Average Fair Value Aggregate Fair Value Outstanding at January 1, 2018 — $ — $ — Transferred in connection with the Separation 157,000 59.85 9,396,455 Vested (8,383 ) 61.49 (515,448 ) Forfeited (1,245 ) 65.18 (81,149 ) Outstanding at December 31, 2018 147,372 $ 59.71 $ 8,799,858 (a) Non-vested shares outstanding at December 31, 2018 included 66,610 shares for EQT employees that will be settled by the Company once vested under the Employee Matters Agreement.
Summary of Option Activity	A summary of option activity as of December 31, 2018 , and changes during the year then ended, is presented below. Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at January 1, 2018 — $ — — $ — Transferred in connection with the Separation 464,876 38.55 — — Exercised — — — — Forfeited — — — — Expired — — — — Outstanding at December 31, 2018 464,876 $ 38.55 5.69 Years $ — Exercisable at December 31, 2018 271,311 $ 40.63 2.45 Years $ —

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of outstanding debt	The following table presents the Company's and its affiliates' outstanding debt as of December 31, 2018 and 2017 . December 31, 2018 December 31, 2017 Principal Carrying Value (a) Fair Value (b) Principal Carrying Value (a) Fair Value (b) (Thousands) Equitrans Midstream Credit Facility $ 16,500 $ 16,500 $ 16,500 $ — $ — $ — EQGP Working Capital Facility with EQT — — — 168 168 168 EQM Credit Facility 625,000 625,000 625,000 180,000 180,000 180,000 RMP Credit Facility — — — 286,000 286,000 286,000 Total credit facility borrowings $ 641,500 $ 641,500 $ 641,500 $ 466,168 $ 466,168 $ 466,168 Equitrans Midstream Term Loans $ 600,000 $ 568,105 $ 589,500 $ — $ — $ — EQM 4.00% Senior Notes due 2024 500,000 495,708 479,950 500,000 494,939 504,110 EQM 4.125% Senior Notes due 2026 500,000 493,264 454,200 500,000 492,413 501,990 EQM 4.75% Senior Notes due 2023 1,100,000 1,089,742 1,099,890 — — — EQM 5.50% Senior Notes due 2028 850,000 839,302 841,526 — — — EQM 6.50% Senior Notes due 2048 550,000 538,623 549,566 — — — Total debt 4,100,000 4,024,744 4,014,632 1,000,000 987,352 1,006,100 Less current portion of debt 6,000 6,000 6,000 — — — Total long-term debt $ 4,094,000 $ 4,018,744 $ 4,008,632 $ 1,000,000 $ 987,352 $ 1,006,100 (a) Carrying value of the senior notes and term loans represents principal amount less unamortized debt issuance costs and debt discounts. (b) See Note 1 for a discussion of fair value measurements.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of summary of income tax expense	The following table summarizes income tax expense for the years ended December 31, 2018, 2017 and 2016 . Years Ended December 31, 2018 2017 2016 (Thousands) Current income tax expense: Federal $ 41,788 $ 43,794 $ 94,068 State 16,108 10,239 21,751 Total current income tax expense 57,896 54,033 115,819 Deferred income tax expense (benefit): Federal 96,499 148,623 (7,892 ) State (71,253 ) 9,746 (9,684 ) Total deferred income tax expense (benefit) 25,246 158,369 (17,576 ) Total income tax expense $ 83,142 $ 212,402 $ 98,243
Schedule of income tax expense reconciliation	The following table summarizes differences between income tax expense and amounts computed at the applicable federal statutory rate on pre-tax income for the years ended December 31, 2018, 2017 and 2016 . Years Ended December 31, 2018 2017 2016 (Thousands) Income tax expense at statutory rate $ 124,828 $ 187,201 $ 169,860 Tax Reform Legislation 7,443 129,266 — State income tax expense 21,827 12,710 7,844 Noncontrolling interests' share of earnings (61,505 ) (116,539 ) (112,672 ) Impairment of goodwill 16,535 — — Rice Midstream Holdings income not subject to tax (26,538 ) (13,460 ) — Regulatory (asset) liability (368 ) 10,488 35,438 Other 920 2,736 (2,227 ) Income tax expense $ 83,142 $ 212,402 $ 98,243 Effective tax rate 14.0 % 39.7 % 20.2 %
Schedule of components of net deferred tax assets and liabilities	The following table summarizes the components of net deferred tax assets. December 31, 2018 2017 (Thousands) Total deferred income tax asset: Net operating loss carryforwards $ 36,202 $ — Investment in partnerships 559,858 257,128 Other 1,261 — Total excluding valuation allowance 597,321 257,128 Valuation allowance — — Total net deferred income tax asset $ 597,321 $ 257,128

Interim Financial Information_2

Interim Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information	The following quarterly summary of operating results reflects variations due primarily to the effect of the Tax Reform Legislation in the three months ended December 31, 2017, the effect of the Rice Merger for the period from November 13, 2017 through December 31, 2018, the effect of increasing separation and other transaction costs related to the EQM-RMP Mergers, the Drop-Down Transaction, the Separation and the EQGP Buyout, the $261.9 million of impairment of goodwill recorded in the fourth quarter of 2018 and the seasonal nature of the Company's transmission and storage business. Three Months Ended March 31 (a) June 30 (a) September 30 (a) December 31 (a)(b) (Thousands, except per share amounts) 2017 Operating revenues $ 200,072 $ 196,815 $ 206,293 $ 292,378 Operating income 144,096 139,178 141,282 118,494 Net income (loss) 118,982 115,885 115,451 (27,861 ) Net income (loss) attributable to Equitrans Midstream 32,269 34,366 33,334 (127,125 ) Earnings (loss) per share of common stock attributable to Equitrans Midstream Basic: Weighted average common stock outstanding 254,432 254,432 254,432 254,432 Net income (loss) $ 0.13 $ 0.14 $ 0.13 $ (0.50 ) Diluted: Weighted average common stock outstanding 255,033 255,033 255,033 254,432 Net income (loss) $ 0.13 $ 0.13 $ 0.13 $ (0.50 ) Three Months Ended March 31 (a) June 30 (a) September 30 (a) December 31 (b) (Thousands, except per share amounts) 2018 Operating revenues $ 371,026 $ 374,697 $ 364,584 $ 384,791 Operating income (loss) 249,340 234,868 218,322 (59,446 ) Net income (loss) 223,744 219,607 185,966 (118,040 ) Net income (loss) attributable to Equitrans Midstream 82,729 101,067 82,825 (48,223 ) Earnings (loss) per share of common stock attributable to Equitrans Midstream Basic: Weighted average common stock outstanding 254,432 254,432 254,432 254,432 Net income (loss) $ 0.33 $ 0.40 $ 0.33 $ (0.19 ) Diluted: Weighted average common stock outstanding 255,033 255,033 255,033 254,432 Net income (loss) $ 0.32 $ 0.40 $ 0.32 $ (0.19 ) (a) For periods prior to the Separation Date, EPS was calculated based on the shares of Equitrans Midstream common stock distributed in connection with the Separation and Distribution and is considered pro forma in nature. Prior to the Separation Date, the Company did not have any issued or outstanding common stock (other than shares owned by EQT). (b) For the quarters ended December 31, 2018 and 2017, because the Company generated a net loss, the Company's computation of EPS excluded potentially dilutive securities; as such, basic and diluted weighted average common stock outstanding were the same for the quarters ended December 31, 2018 and 2017.

Consolidated Variable Interes_2

Consolidated Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Consolidated Variable Interest Entity	The following table summarizes EQM's statements of consolidated operations and cash flows, inclusive of transactions with related parties. Years Ended December 31, 2018 2017 (a) 2016 (Thousands) Operating revenues $ 1,495,098 $ 826,522 $ 732,272 Operating expenses 768,445 245,032 204,416 Other (expenses) income (55,305 ) (9,586 ) 10,098 Net income $ 671,348 $ 571,904 $ 537,954 Net cash provided by operating activities $ 1,187,239 $ 650,550 $ 537,904 Net cash used in investing activities (2,950,254 ) (456,968 ) (732,033 ) Net cash provided by (used in) financing activities 1,725,930 (251,393 ) (106,459 ) (a) Amounts for the year ended December 31, 2017 have not been recast to include the results of the EQM-RMP Mergers and Drop-Down Transaction. The following table presents assets and liabilities included in the Company's consolidated balance sheets that were for the use or obligation of EQM, inclusive of receivables and payables due from or to related parties. December 31, 2018 2017 (a) (Thousands) ASSETS Cash and cash equivalents $ 17,515 $ 2,557 Accounts receivable (a) 254,390 132,108 Other current assets 14,909 12,662 Net property, plant and equipment 5,806,628 2,804,059 Investment in unconsolidated entity 1,510,289 460,546 Goodwill 1,123,813 — Net intangible assets 576,113 — Other assets 152,464 136,895 LIABILITIES Accounts payable (a) $ 207,877 $ 78,713 Capital contribution payable to the MVP Joint Venture 169,202 105,734 Accrued interest 80,199 10,926 Accrued liabilities 20,672 16,871 Credit facility borrowings 625,000 180,000 EQM Senior notes 3,456,639 987,352 Regulatory and other long-term liabilities 38,724 20,273 (a) Amounts as of December 31, 2017 have not been recast to include the results of the EQM-RMP Mergers and Drop-Down Transaction. (b) Accounts receivable and accounts payable as of December 31, 2018 and 2017 included $174.8 million and $103.3 million , respectively, of receivables due from EQT and $34.0 million and $31.7 million , respectively, of payables due to EQT that were for the use or obligation of EQM, respectively, on that date.

Summary of Operations and Sig_4

Summary of Operations and Significant Accounting Policies - Organization Narrative (Details) - USD ($) $ in Millions	Nov. 12, 2018	May 22, 2018	May 01, 2018	Nov. 13, 2017	Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash distributions paid (as a percent)	80.10%
Strike Force Midstream
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Limited partner ownership interest (as a percent)					25.00%
EQT Corporation
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Limited partner ownership interest (as a percent)	19.90%
Strike Force Midstream Holdings LLC | Strike Force Midstream
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Limited partner ownership interest (as a percent)				75.00%
RMP and Gulfport Midstream | Strike Force Midstream
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Limited partner ownership interest (as a percent)			25.00%
EQM | Gulfport Transaction
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash consideration			$ 175
EQM | Drop-Down Transaction
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash consideration		$ 1,150
Common units (in shares)		5,889,282

Summary of Operations and Sig_5

Summary of Operations and Significant Accounting Policies - Nature of Business Narrative (Details) hp in Thousands	Dec. 31, 2018Bcf / dinterstate_pipelineprimary_assetcompressor_stationsystemfacilitygas_reservemihpBcf
Public Utilities, General Disclosures [Line Items]
Number of primary assets through which services are provided | primary_asset	3
Number of independent water service systems | system	2
Length of water pipeline	160
Number of fresh water impoundment facilities | facility	28
Gathering assets
Public Utilities, General Disclosures [Line Items]
Length of pipeline (in miles)	700
Daily capacity (in Bcf per day) | Bcf / d	2.4
Compression capacity (in hp) | hp	333
Length of FERC-regulated lines (in miles)	1,500
Transmission and storage assets
Public Utilities, General Disclosures [Line Items]
Daily capacity (in Bcf per day) | Bcf / d	4.4
Compression capacity (in hp) | hp	120
Length of FERC-regulated lines (in miles)	950
Number of connection points | interstate_pipeline	7
Number of compressor units | compressor_station	41
Number of gas reservoirs | gas_reserve	18
Peak withdrawal capacity (in Bcf per day) | Bcf / d	645
Working gas capacity (in Bcf) | Bcf	43

Summary of Operations and Sig_6

Summary of Operations and Significant Accounting Policies - Significant Accounting Policies Narrative (Details)	Nov. 13, 2017USD ($)reporting_unit	Dec. 31, 2018USD ($)	Dec. 31, 2018USD ($)business_linereporting_unitsegmentshares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)shares	Jan. 01, 2019USD ($)	May 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of business segments | segment			3
Number of lines of business | business_line			3
Accounts receivable, for doubtful accounts		$ 75,000	$ 75,000	$ 446,000
Property, plant and equipment, cost capitalization			54,400,000	46,500,000	$ 53,200,000
Property, plant and equipment, interest capitalization			$ 12,600,000	$ 4,700,000	$ 9,400,000
Property, plant and equipment, depreciation rates			2.70%	1.80%	2.20%
Finite-lived intangible assets, useful life			15 years
Finite-lived intangible assets, accumulated amortization		47,000,000	$ 47,000,000	$ 5,500,000
Finite-lived intangible assets, amortization expense, next five years		41,500,000	41,500,000
Impairment of long-lived assets		0	$ 0	0	$ 59,748,000
Number of reporting units | reporting_unit	2		2
Gas imbalance receivable		3,300,000	$ 3,300,000	5,200,000
Conversion rate for share-based compensation awards transferred			0.80
Accrued incentive compensation		$ 42,100,000	$ 42,100,000
Regulatory asset, amortization period			16 years
Potentially dilutive securities related to stock options and awards (shares) | shares			601,622		601,622
EQM-RMP Mergers
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Intangible assets	$ 623,200,000
RMP
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Intangible assets	$ 623,200,000
Strike Force Midstream
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Limited partner ownership interest (as a percent)		25.00%	25.00%
Interest Expense
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
AFUDC, debt component			$ 1,000,000	800,000	$ 2,400,000
Nonoperating Income (Expense)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
AFUDC, equity component			$ 5,600,000	5,100,000	$ 19,400,000
Minimum | Gathering assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, estimated useful lives			P20Y
Minimum | Transmission and storage assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, estimated useful lives			P20Y
Minimum | Water services assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, estimated useful lives			P10Y
Maximum | Gathering assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, estimated useful lives			P65Y
Maximum | Transmission and storage assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, estimated useful lives			P50Y
Maximum | Water services assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, estimated useful lives			P15Y
EQM | Carrying Value | EES
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated fair value of preferred interest		$ 115,000,000	$ 115,000,000	119,000,000
EQM | Carrying Value | EES | Other Current Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated fair value of preferred interest		4,400,000	4,400,000	4,400,000
EQM | Level 3 | Fair Value | EES
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated fair value of preferred interest		$ 122,000,000	$ 122,000,000	$ 133,000,000
RMP and Gulfport Midstream | Strike Force Midstream
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Limited partner ownership interest (as a percent)							25.00%
Accounting Standards Update 2016-02 | Subsequent Event
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use asset						$ 50,000,000
Lease liability						$ 50,000,000
Phantom Units
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Potentially dilutive securities related to stock options and awards (shares) | shares			161,696	161,696	161,696

Summary of Operations and Sig_7

Summary of Operations and Significant Accounting Policies - Property Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Net property, plant and equipment	$ 5,867,647	$ 5,110,862
Gathering assets
Public Utility, Property, Plant and Equipment [Line Items]
Assets	4,387,908	3,642,937
Accumulated depreciation	(247,720)	(153,791)
Net property, plant and equipment	4,140,188	3,489,146
Transmission and storage assets
Public Utility, Property, Plant and Equipment [Line Items]
Assets	1,785,157	1,674,080
Accumulated depreciation	(286,693)	(248,474)
Net property, plant and equipment	1,498,464	1,425,606
Water services assets
Public Utility, Property, Plant and Equipment [Line Items]
Assets	194,465	193,825
Accumulated depreciation	(26,489)	(3,363)
Net property, plant and equipment	167,976	190,462
Other property, plant and equipment
Public Utility, Property, Plant and Equipment [Line Items]
Net property, plant and equipment	$ 61,019	$ 5,648

Summary of Operations and Sig_8

Summary of Operations and Significant Accounting Policies - Asset Retirement Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation at beginning of period	$ 9,321	$ 0
Liabilities assumed at Rice Merger	0	9,286
Liabilities incurred	231	0
Revisions to estimated liabilities	1,928	0
Accretion expense	455	35
Asset retirement obligation at end of period	$ 11,935	$ 9,321

Summary of Operations and Sig_9

Summary of Operations and Significant Accounting Policies - Regulatory Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Total regulatory assets	$ 26,564	$ 24,951
Regulatory Liabilities [Line Items]
Total regulatory liabilities	20,724	19,902
Deferred taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	10,920	11,318
On-going post-retirement benefits other than pension
Regulatory Liabilities [Line Items]
Total regulatory liabilities	10,132	7,724
Other costs
Regulatory Liabilities [Line Items]
Total regulatory liabilities	(328)	860
Deferred taxes
Regulatory Assets [Line Items]
Total regulatory assets	22,252	18,786
Other costs
Regulatory Assets [Line Items]
Total regulatory assets	$ 4,312	$ 6,165

Summary of Operations and Si_10

Summary of Operations and Significant Accounting Policies - Regulatory Operations and Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement Related Disclosures [Abstract]
Operating revenues	$ 393,911	$ 383,309	$ 343,978
Operating expenses	140,832	143,614	$ 114,978
Public Utility, Property, Plant and Equipment [Line Items]
Net property, plant and equipment	5,867,647	5,110,862
Regulated Operation
Public Utility, Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,900,411	1,787,656
Accumulated depreciation	(317,988)	(278,756)
Net property, plant and equipment	$ 1,582,423	$ 1,508,900

Summary of Operations and Si_11

Summary of Operations and Significant Accounting Policies - Statement of Cash Flow Supplementary Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash paid during the period for:
Interest, net of amount capitalized	$ 54,089	$ 43,797	$ 13,902
Non-cash activity during the period for:
Acquisition of Rice Midstream Holdings LLC	0	3,846,240	0
Settlement of separation and other transaction costs with EQT	133,286	0	0
Net settlement of current income taxes payable with EQT	54,033	115,819	536,871
Elimination of net current and deferred tax liabilities	0	0	1,945
Separation-related adjustments	228,357	0	0
Revision to estimated asset retirement obligations	$ 1,928	$ 0	$ 0

Rice Energy Merger - Narrative

Rice Energy Merger - Narrative (Details) $ in Thousands		Nov. 13, 2018USD ($)	Nov. 13, 2017USD ($)reporting_unit	Dec. 31, 2018USD ($)	Dec. 31, 2018USD ($)reporting_unit	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Goodwill				$ 1,239,269	$ 1,239,269	$ 1,384,872
Number of reporting units | reporting_unit			2		2
Adjustment to purchase price allocation	[1]			210,007	$ 210,007	$ 468,422
Unamortized carryover tax basis of tax-deductible goodwill		$ 387,100
RMP
Business Acquisition [Line Items]
Goodwill			$ 1,501,210	1,239,269	1,239,269
Measurement period adjustments				(20,700)
Adjustment to purchase price allocation				900	900
Adjustment to deferred tax liability			115,456	$ (21,600)	$ (21,600)
Rice Midstream Holdings
Business Acquisition [Line Items]
Goodwill			1,384,900
EQT Corporation | RMP
Business Acquisition [Line Items]
Measurement period adjustments		$ 137,000
Adjustment to deferred tax liability			$ (137,000)
[1]	Accounts receivable as of December 31, 2018 and 2017 included $175.9 million and $158.7 million, respectively of accounts receivable due from EQT, a related party. Accounts payable as of December 31, 2018 and 2017 included $34.1 million and $363.1 million, respectively, of accounts payable due to EQT.

Rice Energy Merger - Assets Acq

Rice Energy Merger - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Nov. 13, 2017	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair value of assets acquired and liabilities assumed:
Goodwill		$ 1,239,269	$ 1,239,269	$ 1,384,872
Impairment of goodwill			261,941	0	$ 0
RMP
Business Acquisition [Line Items]
Enterprise value	$ 3,846,240
Fair value of assets acquired and liabilities assumed:
Current assets	141,410
Property, plant and equipment	2,265,924
Intangible assets	623,200
Other assets	118
Current liabilities	(107,101)
RMP Credit Facility	(266,000)
Due to EQT	187,742			$ 187,700
Deferred income taxes	(115,456)	21,600	21,600
Other long-term liabilities	(9,323)
Total fair value of assets acquired and liabilities assumed	2,345,030
Goodwill	1,501,210	1,239,269	$ 1,239,269
Impairment of goodwill	261,941	$ 261,900
Business combination, fair value of noncontrolling interests assumed	1,500,000
Outstanding principal of debt	187,500
Accrued interest of debt	200
Strike Force Midstream
Fair value of assets acquired and liabilities assumed:
Business combination, fair value of noncontrolling interests assumed	$ 200,000

Rice Energy Merger - Post-Acqui

Rice Energy Merger - Post-Acquisition Operating Results (Details) - RMP $ in Thousands	2 Months Ended
	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Operating revenues	$ 14,881
Operating income attributable to Equitrans Midstream	69,036
Net income attributable to noncontrolling interests	16,644
Net income attributable to Equitrans Midstream	$ 21,814

Rice Energy Merger - Unaudited

Rice Energy Merger - Unaudited Pro Forma Information (Details) - Rice Merger Agreement - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Pro forma operating revenues	$ 1,264,704	$ 997,829
Pro forma net income	549,567	440,735
Pro forma net income attributable to noncontrolling interests	445,576	376,284
Pro forma net income attributable to Equitrans Midstream	$ 103,991	$ 64,451

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Narrative (Details)	12 Months Ended
	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Contract billing cycle	21 days
Water
Disaggregation of Revenue [Line Items]
Contract billing cycle	21 days
Gathering
Disaggregation of Revenue [Line Items]
Weighted average remaining term	11 years
Transmission
Disaggregation of Revenue [Line Items]
Weighted average remaining term	15 years

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Schedule of Disaggregated Revenue Information, by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 384,791	$ 364,584	$ 374,697	$ 371,026	$ 292,378	$ 206,293	$ 196,815	$ 200,072	$ 1,495,098	[1]	$ 895,558	[1]	$ 732,272	[1]
Water service revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									111,227		13,605		0
Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									804,085		755,548		617,053
Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									579,786		126,405		115,219
Gathering
Disaggregation of Revenue [Line Items]
Total operating revenues									997,070		509,967		397,494
Gathering | Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									447,360		407,355		339,237
Gathering | Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									549,710		102,612		58,257
Transmission
Disaggregation of Revenue [Line Items]
Total operating revenues									386,801		371,986		334,778
Transmission | Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									356,725		348,193		277,816
Transmission | Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									30,076		23,793		56,962
Water
Disaggregation of Revenue [Line Items]
Total operating revenues									111,227		13,605		0
Water | Water service revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									111,227		13,605		0
Water | Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									0		0		0
Water | Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues									$ 0		$ 0		$ 0
[1]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of approximately $1.1 billion, $665.9 million and $551.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 8.

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Summary of Remaining Performance Obligations (Details) $ in Thousands	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 893,437
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	967,990
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	974,028
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	968,947
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	929,053
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	4,517,559
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	9,251,014
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 351,028
Remaining performance obligations, expected timing	1 year
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 343,984
Remaining performance obligations, expected timing	1 year
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 340,218
Remaining performance obligations, expected timing	1 year
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 335,137
Remaining performance obligations, expected timing	1 year
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 295,243
Remaining performance obligations, expected timing	1 year
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 2,178,736
Remaining performance obligations, expected timing
Transmission firm reservation fees | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 3,844,346
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 476,709
Remaining performance obligations, expected timing	1 year
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 552,636
Remaining performance obligations, expected timing	1 year
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 562,635
Remaining performance obligations, expected timing	1 year
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 562,635
Remaining performance obligations, expected timing	1 year
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 562,635
Remaining performance obligations, expected timing	1 year
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 2,273,123
Remaining performance obligations, expected timing
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 4,990,373
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 65,700
Remaining performance obligations, expected timing	1 year
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 71,370
Remaining performance obligations, expected timing	1 year
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 71,175
Remaining performance obligations, expected timing	1 year
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 71,175
Remaining performance obligations, expected timing	1 year
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 71,175
Remaining performance obligations, expected timing	1 year
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 65,700
Remaining performance obligations, expected timing
Gathering revenues supported by MVCs | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total firm reservation fees	$ 416,295

Equity (Details)

Equity (Details) - USD ($)	Feb. 05, 2019	Nov. 13, 2018	Nov. 12, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Common stock outstanding (in shares)				$ 254,270,971
Issuance of Equitrans Midstream common stock (in shares)			254,268,864
Preferred share, purchase right (in shares)		$ 1
Preferred stock, maximum acquisition percentage without approval of the board		10.00%
Series A Junior Participating Preferred Stock
Class of Stock [Line Items]
Number of shares each Right holder is entitled to purchase (in percentage)		0.01
Exercise price (in dollars per share)		$ 10,000
Preferred Stock
Class of Stock [Line Items]
Number of shares each Right holder is entitled to purchase (in percentage)		0.01
Common Stock | Rights Agreement, Flip In Transaction
Class of Stock [Line Items]
Exercise price (in dollars per share)		$ 200
Common Stock | Rights Agreement, Exchange Transaction
Class of Stock [Line Items]
Maximum percentage of redemption of repurchase of stock		50.00%
Number of shares authorized to be repurchased (in shares)		1
Common Stock | Rights Agreement, Flip Over Transaction
Class of Stock [Line Items]
Exercise price (in dollars per share)		$ 200
13G Investor
Class of Stock [Line Items]
Preferred stock, maximum acquisition percentage without approval of the board		15.00%
EQT Corporation
Class of Stock [Line Items]
Preferred stock, maximum acquisition percentage without approval of the board		20.00%
The Separation and Distribution Agreement | EQT Corporation
Class of Stock [Line Items]
Common stock outstanding (in shares)			$ 254,586,700
Subsequent Event
Class of Stock [Line Items]
Cash dividends declared (in dollars per share)	$ 0.41
EQT Corporation
Class of Stock [Line Items]
Common stock outstanding (in shares)				$ 50,599,503

Financial Information by Busi_3

Financial Information by Business Segment - Narrative (Details)	12 Months Ended
	Dec. 31, 2018business_linesegment
Segment Reporting [Abstract]
Number of business segments | segment	3
Number of lines of business | business_line	3

Financial Information by Busi_4

Financial Information by Business Segment - Schedule of Segment Information (Details) - USD ($) $ in Thousands		Nov. 13, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016		Nov. 13, 2018	Dec. 31, 2015
Revenues from external customers (including related parties):
Total operating revenues			$ 384,791	$ 364,584	$ 374,697	$ 371,026	$ 292,378	$ 206,293	$ 196,815	$ 200,072	$ 1,495,098	[1]	$ 895,558	[1]	$ 732,272	[1]
Operating income (loss):
Total operating income			(59,446)	218,322	234,868	249,340	118,494	141,282	139,178	144,096	643,084		543,050		465,066
Reconciliation of operating income to net income:
Equity income	[2]										61,778		22,171		9,898
Other income											5,011		4,439		27,113
Net interest expense	[3]										115,454		34,801		16,761
Income tax expense											83,142		212,402		98,243
Net income			(118,040)	$ 185,966	$ 219,607	$ 223,744	(27,861)	$ 115,451	$ 115,885	$ 118,982	511,277		322,457		387,073
Impairment of goodwill											261,941		0		0
Segment assets:
Total assets			10,523,835				8,328,796				10,523,835		8,328,796
Depreciation:
Total											(175,821)		(96,674)		(62,691)
Expenditures for segment assets:
Total											884,574		371,857		587,364
Accrued capital expenditures			109,300				90,700				109,300		90,700		26,700			$ 24,100
RMP
Reconciliation of operating income to net income:
Impairment of goodwill		$ 261,941	261,900
Expenditures for segment assets:
Accrued capital expenditures assumed in acquisition																	$ 72,300
Gathering
Revenues from external customers (including related parties):
Total operating revenues											997,070		509,967		397,494
Gathering | RMP
Reconciliation of operating income to net income:
Impairment of goodwill			261,900
Transmission
Revenues from external customers (including related parties):
Total operating revenues											386,801		371,986		334,778
Water
Revenues from external customers (including related parties):
Total operating revenues											111,227		13,605		0
Operating segments
Segment assets:
Total assets			9,315,915				7,811,933				9,315,915		7,811,933
Operating segments | Gathering
Revenues from external customers (including related parties):
Total operating revenues											997,070		509,967		397,494
Operating income (loss):
Total operating income											423,407		369,093		289,643
Segment assets:
Total assets			6,011,654				5,656,094				6,011,654		5,656,094
Depreciation:
Total											(98,678)		(44,957)		(30,422)
Expenditures for segment assets:
Total											717,251		254,522		295,315
Operating segments | Transmission
Revenues from external customers (including related parties):
Total operating revenues											386,801		371,986		334,778
Operating income (loss):
Total operating income											265,579		247,467		238,213
Segment assets:
Total assets			3,066,659				1,947,566				3,066,659		1,947,566
Depreciation:
Total											(49,723)		(58,689)		(32,269)
Expenditures for segment assets:
Total											114,450		111,102		292,049
Operating segments | Water
Revenues from external customers (including related parties):
Total operating revenues											111,227		13,605		0
Operating income (loss):
Total operating income											37,667		4,145		0
Segment assets:
Total assets			237,602				208,273				237,602		208,273
Depreciation:
Total											(23,513)		(3,515)		0
Expenditures for segment assets:
Total											23,537		6,233		0
Other/Headquarters
Operating income (loss):
Total operating income											(83,569)		(77,655)		(62,790)
Reconciliation of operating income to net income:
Income tax expense													10,500
Segment assets:
Total assets			$ 1,207,920				$ 516,863				1,207,920		516,863
Depreciation:
Total											(3,907)		10,487		0
Expenditures for segment assets:
Total											$ 29,336		$ 0		$ 0
[1]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of approximately $1.1 billion, $665.9 million and $551.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 8.
[2]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 7.
[3]	Net interest expense included interest income on the Preferred Interest (defined in Note 1) of $6.6 million, $6.8 million and $1.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. Other income included distributions received from EES (defined in Note 1) of $8.3 million for the year ended December 31, 2016. See Note 1.

Investments in Consolidated, _3

Investments in Consolidated, Non-Wholly-Owed Entities - Investment in EQGP (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2018	Nov. 29, 2018	May 22, 2018	Dec. 31, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Purchase of EQGP common units					$ (291,206)
EQGP | Limited Partner Common
Class of Stock [Line Items]
Partners' capital common units outstanding (in shares)	290,569,047			290,569,047	290,569,047
Limited partner ownership interest (as a percent)	96.10%
Unit Purchase Agreements
Class of Stock [Line Items]
Aggregate purchase price	$ 291,200
Unit Purchase Agreements | EQGP
Class of Stock [Line Items]
Number of units purchased (in shares)				14,560,281
Unit Purchase Agreements | EQGP | Neuberger Berman Investment Adviser LP
Class of Stock [Line Items]
Number of units purchased (in shares)		5,842,704
Price per common unit (in dollars per unit)		$ 20
Unit Purchase Agreements | EQGP | Goldman Sachs Asset Management, L.P.
Class of Stock [Line Items]
Number of units purchased (in shares)		1,865,020
Unit Purchase Agreements | EQGP | Cushing Asset Management LP
Class of Stock [Line Items]
Number of units purchased (in shares)		920,130
Unit Purchase Agreements | EQGP | Kayne Anderson Capital Advisors, L.P.
Class of Stock [Line Items]
Number of units purchased (in shares)		1,363,974
Unit Purchase Agreements | EQGP | ZP Energy Fund, L.P.
Class of Stock [Line Items]
Number of units purchased (in shares)		5,372,593
EQGP | RMP IDR Transaction
Class of Stock [Line Items]
Number of units purchased (in shares)			36,293,766
Common Stock
Class of Stock [Line Items]
Purchase of EQGP common units					$ (46,764)
Noncontrolling Interests
Class of Stock [Line Items]
Purchase of EQGP common units					$ (244,400)

Investments in Consolidated, _4

Investments in Consolidated, Non-Wholly-Owed Entities - Investment in EQM (Details) $ / shares in Units, $ in Millions	Feb. 13, 2019USD ($)shares	Feb. 01, 2019USD ($)	Jan. 17, 2019USD ($)$ / shares	Jul. 23, 2018shares	May 22, 2018shares	Sep. 30, 2015USD ($)	Dec. 31, 2018$ / sharesshares	Dec. 31, 2017shares	Dec. 31, 2016USD ($)$ / sharesshares
EQM | Limited Partner Common
Schedule of Equity Method Investments [Line Items]
Partners' capital common units outstanding (in shares)							15,433,812
Limited partner ownership interest (as a percent)							12.70%
EQM | Limited Partner Common | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Partners' capital common units outstanding (in shares)	117,245,455
Limited partner ownership interest (as a percent)	59.90%
EQM-RMP Mergers
Schedule of Equity Method Investments [Line Items]
Common units (in shares)				102,323,796
EQGP | EQM | Limited Partner Common
Schedule of Equity Method Investments [Line Items]
Partners' capital common units outstanding (in shares)							21,811,643
Limited partner ownership interest (as a percent)							17.90%
EQGP | EQM | General Partner Units
Schedule of Equity Method Investments [Line Items]
Number of general partner units (in shares)							1,443,015
General partner ownership interest (as a percent)							1.20%
EQM
Schedule of Equity Method Investments [Line Items]
At the market program | $						$ 750
Common units (in shares)							0	0	2,949,309
Average price per unit (in shares) | $ / shares									$ 74.42
Proceeds from the issuance of EQM common units, net of offering costs | $									$ 217.1
Underwriter's discount and other offering expenses | $									2.4
Commissions | $									$ 2.2
Incremental cash distributions (percentage)							48.00%
Incremental cash distribution, after distribution per share to common and general partners (USD per share) | $ / shares							$ 0.5250
EQM | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Cash distributions paid per unit (in dollars per share) | $ / shares			$ 1.13
Cash distributions declared per unit (in dollars per share) | $			$ 211.3
Cash distributions paid | $		$ 117.3
Incentive distribution | $	$ 72.7
EQM | General Partner Units | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Cash distributions paid | $	2.5
EQM | Limited Partner | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Cash distributions paid | $	$ 42.1
EQM | Phantom Units
Schedule of Equity Method Investments [Line Items]
Common share converted (in shares)				12,024
EQM | Drop-Down Transaction
Schedule of Equity Method Investments [Line Items]
Common units (in shares)					5,889,282
EQM | EQM-RMP Mergers
Schedule of Equity Method Investments [Line Items]
Common units (in shares)				33,963,753
Exchange rate				0.3319
EQM | EQM-RMP Mergers | Phantom Units
Schedule of Equity Method Investments [Line Items]
Common units (in shares)				36,220
RMP | EQM-RMP Mergers
Schedule of Equity Method Investments [Line Items]
Common units (in shares)				28,757,246
Exchange rate				0.3319
Common share converted (in shares)				9,544,530

Investments in Consolidated, _5

Investments in Consolidated, Non-Wholly-Owed Entities - Net Changes in Ownership of EQGP and EQM (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2018	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities		$ 55,669	$ (16,191)
$750 ATM Program
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities			(15,900)
EQM
Schedule of Equity Method Investments [Line Items]
At the market program	$ 750,000
Parent Net Investment
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities		(159,255)	24,296
Parent Net Investment | $750 ATM Program
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities			24,000
Parent Net Investment | Drop-Down Transaction
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities		16,000
Parent Net Investment | RMP IDR Transaction
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities		(35,000)
Parent Net Investment | EQM-RMP Mergers
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities		(140,000)
Noncontrolling Interests
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities		$ 214,924	(40,487)
Noncontrolling Interests | $750 ATM Program
Schedule of Equity Method Investments [Line Items]
Net changes in ownership of consolidated entities			$ (39,900)

Investments in Unconsolidated_3

Investments in Unconsolidated Entity - Narrative (Details) $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Mar. 31, 2019USD ($)	Jan. 31, 2019USD ($)	Dec. 31, 2018USD ($)mi	Nov. 30, 2018USD ($)	Dec. 31, 2018USD ($)mi	Dec. 31, 2018USD ($)mi	Feb. 28, 2019USD ($)	Sep. 30, 2018	Apr. 30, 2018mi	Jan. 31, 2016
MVP
Schedule of Equity Method Investments [Line Items]
Length of pipeline (in miles) | mi			300		300	300
MVP Southgate Project
Schedule of Equity Method Investments [Line Items]
Length of pipeline (in miles) | mi									70
Variable Interest Entity, Not Primary Beneficiary | MVP | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee, remaining capital obligation, percentage		33.00%
Variable Interest Entity, Not Primary Beneficiary | MVP Southgate Project | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee, remaining capital obligation, percentage							33.00%
Variable Interest Entity, Not Primary Beneficiary | MVP Southgate Project | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee							$ 14
Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Capital call notice				$ 167.4
Maximum financial statement exposure			$ 1,700		$ 1,700	$ 1,700
Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Capital call notice, funds received	$ 24.4
Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Capital call notice, funds received		$ 143
Variable Interest Entity, Not Primary Beneficiary | MVP Southgate Project
Schedule of Equity Method Investments [Line Items]
Capital call notice			$ 1.8
EQM
Schedule of Equity Method Investments [Line Items]
Purchase of additional ownership interest					$ 11.3
EQM | Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Decrease in ownership interest (as a percent)										8.50%
Ownership interest			45.50%		45.50%	45.50%
EQM | Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee		$ 261
EQM | Variable Interest Entity, Not Primary Beneficiary | MVP Southgate Project
Schedule of Equity Method Investments [Line Items]
Ownership interest			47.20%		47.20%	47.20%		32.70%
Beneficial Owner | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest						66.67%

Investments in Unconsolidated_4

Investments in Unconsolidated Entity - Schedule of Unaudited Condensed Financial Statements for the Investment in Unconsolidated Equity (Details) - MVP Joint Venture - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Consolidated Balance Sheets
Current assets	$ 687,657	$ 330,271
Noncurrent assets	3,223,220	747,728
Total assets	3,910,877	1,077,999
Current liabilities	617,355	65,811
Equity	3,293,522	1,012,188
Total liabilities and equity	3,910,877	1,077,999
Condensed Statements of Consolidated Operations
AFUDC – equity	91,056	32,054	$ 16,315
Net interest income	44,786	16,674	5,206
Net income	$ 135,842	$ 48,728	$ 21,521

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) - USD ($)	2 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2018	Nov. 12, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 13, 2018
Related Party Transaction [Line Items]
Separation and other transaction costs			$ 53,272,000	$ 85,124,000	$ 0
EQGP | EQGP Working Capital Facility with EQT | EQT Corporation | Line of credit
Related Party Transaction [Line Items]
Maximum borrowing capacity		$ 50,000,000				$ 20,000,000
Line of credit outstanding	$ 1,000,000		1,000,000
Maximum outstanding borrowing	3,300,000
Average daily balance of short term loans outstanding	$ 900,000	$ 200,000		$ 100,000	$ 100,000
Weighted average annual interest rate	4.10%
Drop-Down Transaction, EQM-RMP Mergers and Separation Transactions
Related Party Transaction [Line Items]
Separation and other transaction costs			$ 39,600,000
Basis for allocation of transaction cost (in percent)			50.00%

Related Party Transactions - Su

Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Operating revenues		$ 1,111,289	$ 665,939	$ 551,353
Operating and maintenance expense		49,778	40,601	34,179
Selling, general and administrative expense		85,081	75,610	70,387
Separation and other transaction costs		53,272	85,124	0
Equity income	[1]	61,778	22,171	9,898
Other income from the Preferred Interest		0	0	8,293
Interest income from the Preferred Interest		6,578	6,818	1,740
Net interest expense		5	(2,120)	3
Net (payments on) proceeds from EQGP's working capital loan with EQT		(168)	84	18
Capital contributions to the MVP Joint Venture		(913,195)	(159,550)	(98,399)
Principal payments received on the Preferred Interest		4,406	4,166	1,024
Net (distributions to) contributions from EQT		(701,901)	(893,682)	$ 740,797
Rice Merger Transaction
Related Party Transaction [Line Items]
Separation and other transaction costs		$ 13,700	85,100
Interest expense			$ 2,900
[1]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 7.

Related Party Transactions - _2

Related Party Transactions - Summary of Due To (From) Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Related Party Transactions [Abstract]
Accounts receivable – related parties	$ 175,869	$ 158,720
Investment in unconsolidated entity	1,510,289	460,546
Preferred Interest	114,720	119,127
Accounts payable – related parties	34,071	363,058
Capital contribution payable to the MVP Joint Venture	$ 169,202	$ 105,734

Share-based Compensation Plan_2

Share-based Compensation Plans - Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 23, 2018shares	Jul. 23, 2018USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion rate for share-based compensation awards transferred			0.80
Share-based compensation expense | $			$ 10,576	$ 500	$ 400
EQM | EQM-RMP Mergers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exchange rate	0.3319	0.3319
RMP | EQM-RMP Mergers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exchange rate	0.3319	0.3319
VDPSU Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award requisite service period			1 year
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award requisite service period			36 months
Performance Shares | 2017 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $			$ 300
Awards outstanding (in shares)			35,728
Performance Shares | 2017 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $			$ 1,600
Awards outstanding (in shares)			84,014
Performance Shares | 2018 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $			$ 300
Awards outstanding (in shares)			85,872
Performance Shares | 2018 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $			$ 2,200
Awards outstanding (in shares)			100,435
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout factor			0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout factor			300.00%
Performance Shares, Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term for risk-free rate			3 years
Performance Shares, Liability Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term for risk-free rate			2 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $			$ 1,048
Unrecognized compensation cost | $			$ 2,000
Period after which the shares granted will be fully vested			3 years
Weighted average vesting term			1 year 3 months 22 days
Awards outstanding (in shares)			147,372	0
Number of shares granted (in shares)			157,000
Weighted average fair value, awards granted (in dollars per share) | $ / shares			$ 59.71	$ 0
Number of shared outstanding and vested (in shares)			8,383
Restricted Stock Units, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period after which the shares granted will be fully vested			3 years
Awards outstanding (in shares)			510,328
Total liability awards | $			$ 4,500
Restricted Stock Units, Liability | EQT Corporation
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares transfered (in shares)			513,413
Number of shares transfered, that were forfeited (in shares)			3,085
Nonqualified Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $			$ 201
Unrecognized compensation cost | $			$ 300
Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted (in shares)			41,880
Weighted average fair value, awards granted (in dollars per share) | $ / shares			$ 21.51
Phantom Units | EQM-RMP Mergers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $		$ 900
Phantom Units | EQGP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $			$ 300	$ 300	$ 200
Awards outstanding (in shares)			21,289
Number of shares granted (in shares)			10,560	8,940	8,270
Weighted average fair value, awards granted (in dollars per share) | $ / shares			$ 26.28	$ 25.21	$ 21.57
Phantom Units | EQM
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $			$ 400	$ 200	$ 200
Awards outstanding (in shares)			17,470
Number of shares granted (in shares)			5,100	2,940	2,610
Weighted average fair value, awards granted (in dollars per share) | $ / shares			$ 68.66	$ 76.68	$ 75.46
Phantom Units | EQM | EQM-RMP Mergers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units converted (in shares)	12,024
Phantom Units | RMP | EQM-RMP Mergers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award requisite service period			1 year
Number of shared outstanding and vested (in shares)	36,220
First anniversary of the grant date | VDPSU Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			50.00%
Second anniversary of the grant date | VDPSU Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			50.00%
EQT Employees | Performance Shares | 2017 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)			30,112
EQT Employees | Performance Shares | 2017 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)			46,297
EQT Employees | Performance Shares | 2018 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)			58,160
EQT Employees | Performance Shares | 2018 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)			54,643
EQT Employees | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)			66,610
EQT Employees | Restricted Stock Units, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)			296,616

Share-based Compensation Plan_3

Share-based Compensation Plans - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 10,576	$ 500	$ 400
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	1,048
Non-qualified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	201
Other programs, including non-employee director awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	2,678
2016 EQT Incentive Performance Share Unit Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	956
2017 EQT Incentive Performance Share Unit Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	1,642
2018 EQT Incentive Performance Share Unit Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	906
2017 EQT Value Driver Performance Share Unit Award Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	255
2018 EQT Value Driver Performance Share Unit Award Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 2,890

Share-based Compensation Plan_4

Share-based Compensation Plans - Schedule of Executive Performance Incentive Programs (Details) - Performance Shares	12 Months Ended
	Dec. 31, 2018$ / sharesshares
2016 EQT Incentive Performance Share Unit Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 109.30
Risk Free Rate	1.31%
Awards Outstanding (in shares)	307,553
2017 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 120.60
Risk Free Rate	1.47%
Awards Outstanding (in shares)	35,728
2017 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 59.90
Risk Free Rate	2.61%
Awards Outstanding (in shares)	84,014
2018 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 76.53
Risk Free Rate	1.97%
Awards Outstanding (in shares)	85,872
2018 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 33.87
Risk Free Rate	2.46%
Awards Outstanding (in shares)	100,435
EQT Employees | 2016 EQT Incentive Performance Share Unit Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	203,238
EQT Employees | 2017 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	30,112
EQT Employees | 2017 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	46,297
EQT Employees | 2018 Incentive Performance Share Unit Program, Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	58,160
EQT Employees | 2018 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	54,643

Share-based Compensation Plan_5

Share-based Compensation Plans - Schedule of Compensation Costs by Performance Incentive Plan (Details) - Performance Shares	12 Months Ended
	Dec. 31, 2018USD ($)
2016 EQT Incentive Performance Share Unit Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs capitalized	$ 80,800
2017 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs capitalized	1,046,800
2018 Incentive Performance Share Unit Program, Liability
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs capitalized	$ 304,900

Share-based Compensation Plan_6

Share-based Compensation Plans - Summary of Valuation Assumptions for Incentive Performance Plan (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Performance Shares, Liability Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	2.46%	2.61%
Volatility factor	35.70%	41.17%
Expected term	2 years	1 year
Performance Shares, Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.97%	1.47%	1.31%
Volatility factor	32.60%	32.30%	28.43%
Expected term	3 years	3 years	3 years

Share-based Compensation Plan_7

Share-based Compensation Plans - Schedule of Value Driver Award Programs (Details) - Value Driver Award	12 Months Ended
	Dec. 31, 2018$ / sharesshares
2017 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 20.02
Awards Outstanding (in shares)	170,966
2018 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value (in dollars per share) | $ / shares	$ 20.02
First Tranche First Quarter of 2019 | 2018 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	205,420
Second Tranche First Quarter of 2020 | 2018 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	205,781
EQT Employees | 2017 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	94,488
EQT Employees | 2018 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding (in shares)	194,460

Share-based Compensation Plan_8

Share-based Compensation Plans - Schedule of Compensation Costs by Value Driver Award Programs (Details) - Value Driver Award	12 Months Ended
	Dec. 31, 2018USD ($)
2017 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs capitalized	$ 955,400
2018 EQT VDPSU Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation costs capitalized	$ 1,903,200

Share-based Compensation Plan_9

Share-based Compensation Plans - Summary of Restricted Stock Activity (Details) - Restricted Stock	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Non-vested Shares
Outstanding, beginning balance (in shares)	0
Transferred in connection with the Separation (in shares)	157,000
Number of shared outstanding and vested (in shares)	(8,383)
Number of share forfeited (in shares)	(1,245)
Outstanding, ending balance (in shares)	147,372
Weighted Average Fair Value
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 0
Transferred in connection with the Separation (in dollars per share) | $ / shares	59.85
Vested (in dollars per share) | $ / shares	61.49
Forfeited (in dollars per share) | $ / shares	65.18
Outstanding, ending balance (in dollars per share) | $ / shares	$ 59.71
Aggregate Fair Value
Outstanding at December 31, 2018 | $	$ 0
Transferred in connection with the Separation | $	9,396,455
Vested | $	(515,448)
Forfeited | $	(81,149)
Outstanding at December 31, 2018 | $	$ 8,799,858
EQT Employees
Non-vested Shares
Outstanding, ending balance (in shares)	66,610

Share-based Compensation Pla_10

Share-based Compensation Plans - Schedule of Valuation Assumptions for Non-Qualified Stock Options (Details) - Nonqualified Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	2.25%	1.95%	1.67%
Dividend Yield	0.20%	0.18%	0.16%
Volatility factor	26.46%	27.45%	28.59%
Expected term	5 years	5 years	5 years
Number of options granted in conjunction with the separation (in shares)	57,440	32,560	105,600
Weighted average grant date fair value (in dollars per share)	$ 8.55	$ 9.89	$ 8.53
Total intrinsic value of options exercised (millions)	$ 0	$ 0	$ 0

Share-based Compensation Pla_11

Share-based Compensation Plans - Summary of Non-Qualified Option Activity (Details) - Nonqualified Stock Options	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Shares
Outstanding, beginning balance (in shares) | shares	0
Transferred in connection with the Separation (in shares) | shares	464,876
Exercised (in shares) | shares	0
Forfeited (in shares) | shares	0
Expired (in shares) | shares	0
Outstanding, ending balance (in shares) | shares	464,876
Exercisable (in shares) | shares	271,311
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 0
Transferred in connection with the Separation (in dollars per share) | $ / shares	38.55
Exercised (in dollars per share) | $ / shares	0
Forfeited (in dollars per share) | $ / shares	0
Expired (in dollars per share) | $ / shares	0
Outstanding, ending balance (in dollars per share) | $ / shares	38.55
Weighted average exercise price, exercisable (in dollars per share) | $ / shares	$ 40.63
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, outstanding	5 years 8 months 9 days
Weighted average remaining contractual term, exercisable	2 years 5 months 12 days
Aggregate Intrinsic Value, outstanding, end of period | $	$ 0
Aggregate Intrinsic Value, exercisable, end of period | $	$ 0

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Less current portion of debt	$ 6,000,000	$ 0
Line of credit
Debt Instrument [Line Items]
Principal	641,500,000	466,168,000
Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Principal	16,500,000	0
Line of credit | EQGP Working Capital Facility with EQT
Debt Instrument [Line Items]
Principal	0	168,000
Line of credit | EQM Credit Facility
Debt Instrument [Line Items]
Principal	625,000,000	180,000,000
Line of credit | RMP Credit Facility
Debt Instrument [Line Items]
Principal	0	286,000,000
Term Loans | Equitrans Midstream Term Loans
Debt Instrument [Line Items]
Principal	600,000,000	0
EQM Senior notes | EQM 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Principal	$ 500,000,000	500,000,000
Interest rate (as a percent)	4.00%
EQM Senior notes | EQM 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Principal	$ 500,000,000	500,000,000
Interest rate (as a percent)	4.125%
EQM Senior notes | EQM 4.75% Senior Notes due 2023
Debt Instrument [Line Items]
Principal	$ 1,100,000,000	0
Interest rate (as a percent)	4.75%
EQM Senior notes | EQM 5.50% Senior Notes due 2028
Debt Instrument [Line Items]
Principal	$ 850,000,000	0
Interest rate (as a percent)	5.50%
EQM Senior notes | EQM 6.50% Senior Notes due 2048
Debt Instrument [Line Items]
Principal	$ 550,000,000	0
Interest rate (as a percent)	6.50%
Notes and Loans Payable
Debt Instrument [Line Items]
Principal	$ 4,100,000,000	1,000,000,000
Less current portion of debt	6,000,000	0
Total long-term debt	4,094,000,000	1,000,000,000
Carrying Value | Line of credit
Debt Instrument [Line Items]
Carrying Value	641,500,000	466,168,000
Carrying Value | Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Carrying Value	16,500,000	0
Carrying Value | Line of credit | EQGP Working Capital Facility with EQT
Debt Instrument [Line Items]
Carrying Value	0	168,000
Carrying Value | Line of credit | EQM Credit Facility
Debt Instrument [Line Items]
Carrying Value	625,000,000	180,000,000
Carrying Value | Line of credit | RMP Credit Facility
Debt Instrument [Line Items]
Carrying Value	0	286,000,000
Carrying Value | Term Loans | Equitrans Midstream Term Loans
Debt Instrument [Line Items]
Carrying Value	568,105,000	0
Carrying Value | EQM Senior notes | EQM 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Carrying Value	495,708,000	494,939,000
Carrying Value | EQM Senior notes | EQM 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Carrying Value	493,264,000	492,413,000
Carrying Value | EQM Senior notes | EQM 4.75% Senior Notes due 2023
Debt Instrument [Line Items]
Carrying Value	1,089,742,000	0
Carrying Value | EQM Senior notes | EQM 5.50% Senior Notes due 2028
Debt Instrument [Line Items]
Carrying Value	839,302,000	0
Carrying Value | EQM Senior notes | EQM 6.50% Senior Notes due 2048
Debt Instrument [Line Items]
Carrying Value	538,623,000	0
Carrying Value | Notes and Loans Payable
Debt Instrument [Line Items]
Carrying Value	4,024,744,000	987,352,000
Less current portion of debt	6,000,000	0
Total long-term debt	4,018,744,000	987,352,000
Fair Value | Line of credit
Debt Instrument [Line Items]
Fair Value	641,500,000	466,168,000
Fair Value | Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Fair Value	16,500,000	0
Fair Value | Line of credit | EQGP Working Capital Facility with EQT
Debt Instrument [Line Items]
Fair Value	0	168,000
Fair Value | Line of credit | EQM Credit Facility
Debt Instrument [Line Items]
Fair Value	625,000,000	180,000,000
Fair Value | Line of credit | RMP Credit Facility
Debt Instrument [Line Items]
Fair Value	0	286,000,000
Fair Value | Term Loans | Equitrans Midstream Term Loans
Debt Instrument [Line Items]
Fair Value	589,500,000	0
Fair Value | EQM Senior notes | EQM 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Fair Value	479,950,000	504,110,000
Fair Value | EQM Senior notes | EQM 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Fair Value	454,200,000	501,990,000
Fair Value | EQM Senior notes | EQM 4.75% Senior Notes due 2023
Debt Instrument [Line Items]
Fair Value	1,099,890,000	0
Fair Value | EQM Senior notes | EQM 5.50% Senior Notes due 2028
Debt Instrument [Line Items]
Fair Value	841,526,000	0
Fair Value | EQM Senior notes | EQM 6.50% Senior Notes due 2048
Debt Instrument [Line Items]
Fair Value	549,566,000	0
Fair Value | Notes and Loans Payable
Debt Instrument [Line Items]
Fair Value	4,014,632,000	1,006,100,000
Less current portion of debt	6,000,000	0
Total long-term debt	$ 4,008,632,000	$ 1,006,100,000

Debt - Debt Maturity (Details)

Debt - Debt Maturity (Details) $ in Billions	Dec. 31, 2018USD ($)
Debt Disclosure [Abstract]
Payments in 2023	$ 1.1
Payments in 2024 and thereafter	$ 3

Debt - Equitrans Midstream Cred

Debt - Equitrans Midstream Credit Facility (Details)	1 Months Ended	2 Months Ended
	Oct. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Letters of credit outstanding		$ 641,500,000	$ 466,000,000
Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 100,000,000
Available additional borrowings	$ 200,000,000
Consolidated leverage ratio	3.50
Letters of credit outstanding		0
Maximum amount of short term loans outstanding		16,500,000
Average daily balance of short term loans outstanding		$ 7,400,000
Weighted average annual interest rate (as a percent)		4.20%
Same-day swing line advances | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 25,000,000
Letter of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000,000
Base Rate | Minimum | Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%
Base Rate | Maximum | Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%
Eurodollar | Minimum | Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Eurodollar | Maximum | Line of credit | Equitrans Midstream Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%

Debt - Equitrans Midstream Term

Debt - Equitrans Midstream Term Loan Facility (Details)	Dec. 31, 2018USD ($)	Mar. 31, 2019	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Scenario, Forecast
Debt Instrument [Line Items]
Debt service coverage ratio		1.10
Term Loans | Equitrans Midstream Term Loans
Debt Instrument [Line Items]
Principal	$ 600,000,000		$ 600,000,000	$ 0
Net proceeds from offering	568,100,000
Discount	18,000,000		18,000,000
Debt issuance costs	$ 13,900,000		$ 13,900,000
Aggregate annual amount due			1.00%
Periodic quarterly payment			$ 6,000,000
Incremental borrowing capacity			$ 150,000,000
Term Loans | Equitrans Midstream Term Loans | Maximum
Debt Instrument [Line Items]
Repayment ratio subject to variable percentage of excess cash flow			50.00%
Term Loans | Equitrans Midstream Term Loans | Minimum
Debt Instrument [Line Items]
Repayment ratio subject to variable percentage of excess cash flow			0.00%
Term Loans | Equitrans Midstream Term Loans | Federal Funds Effective Rate
Debt Instrument [Line Items]
Basis spread above commitment fee			0.50%
Term Loans | Equitrans Midstream Term Loans | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread above commitment fee			1.00%
Term Loans | Equitrans Midstream Term Loans | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Basis spread above commitment fee			4.50%
Term Loans | Equitrans Midstream Term Loans | Alternate Base Rate
Debt Instrument [Line Items]
Basis spread above commitment fee			3.50%

Debt - EQGP Working Capital Fac

Debt - EQGP Working Capital Facility with EQT (Details) - Line of credit - EQGP Working Capital Facility with EQT - EQT Corporation - EQGP - USD ($)	Nov. 12, 2018	Dec. 31, 2018	Nov. 12, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 13, 2018
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 50,000,000		$ 50,000,000			$ 20,000,000
Repayments of debt	$ 3,200,000
Maximum amount of short term loans outstanding			3,200,000	$ 300,000	$ 200,000
Average daily balance of short term loans outstanding		$ 900,000	$ 200,000	$ 100,000	$ 100,000
Weighted average annual interest rate (as a percent)			3.50%	2.50%	2.00%

Debt - EQM Credit Facility (Det

Debt - EQM Credit Facility (Details)	1 Months Ended	12 Months Ended
	Oct. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2018USD ($)
Debt Instrument [Line Items]
Letters of credit outstanding		$ 641,500,000	$ 466,000,000
EQM | EQM Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Letters of credit outstanding		$ 1,000,000	0
Line of credit | EQM | $3 Billion Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 3,000,000,000
Additional available borrowings	750,000,000
Line of credit | EQM | EQM Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 1,000,000,000
Consolidated leverage ratio		5
Consolidated leverage ratio for certain measurement periods		5.50
Maximum amount of short term loans outstanding		$ 674,000,000	260,000,000	$ 401,000,000
Average daily balance of short term loans outstanding		$ 230,000,000	$ 74,000,000	$ 77,000,000
Weighted average annual interest rate (as a percent)		3.60%	2.80%	2.00%
Debt related commitment fees		$ 2,800,000	$ 1,800,000	$ 1,600,000
Same-day swing line advances | EQM | $3 Billion Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	250,000,000
Letter of credit | EQM | $3 Billion Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000,000
Minimum | Base Rate | Line of credit | EQM | EQM Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	0.125%
Minimum | Eurodollar | Line of credit | EQM | EQM Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	1.125%
Maximum | Base Rate | Line of credit | EQM | EQM Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	0.875%
Maximum | Eurodollar | Line of credit | EQM | EQM Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate	1.875%

Debt - EQM 364-Day Facility (De

Debt - EQM 364-Day Facility (Details) - EQM - Revolving Credit Facility - USD ($)	Nov. 12, 2018	Nov. 12, 2018	Dec. 31, 2017	Dec. 31, 2016
$500 Million Uncommitted Revolving Loan Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 500,000,000	$ 500,000,000
Line of credit expiration period		364 days	364 days
Borrowings outstanding			$ 0	$ 0
Maximum amount of short term loans outstanding		$ 0	100,000,000
Average daily balance of short term loans outstanding			$ 23,000,000
Weighted average annual interest rate (as a percent)			2.20%
Line of credit
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.10%

Debt - EQM Term Loan Facility (

Debt - EQM Term Loan Facility (Details) - Line of credit - $2.5 Billion Senior Notes - EQM - USD ($)	Jun. 25, 2018	Jun. 25, 2018	Nov. 12, 2018	Jun. 30, 2018	Apr. 30, 2018
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 2,500,000,000	$ 2,500,000,000		$ 2,500,000,000	$ 2,500,000,000
Line of credit expiration period			364 days
Debt issuance costs	$ 3,000,000
Maximum amount of short term loans outstanding		1,825,000,000
Average daily balance of short term loans outstanding		$ 1,231,000,000
Weighted average annual interest rate (as a percent)		3.30%

Debt - EQM $2.5 Billion Senior

Debt - EQM $2.5 Billion Senior Notes (Details) - USD ($)	1 Months Ended
	Jun. 30, 2018	Dec. 31, 2018	Jun. 25, 2018	Apr. 30, 2018	Dec. 31, 2017
EQM 4.75% Senior Notes due 2023 | EQM Senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)		4.75%
Principal		$ 1,100,000,000			$ 0
EQM 5.50% Senior Notes due 2028 | EQM Senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)		5.50%
Principal		$ 850,000,000			0
EQM 6.50% Senior Notes due 2048 | EQM Senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)		6.50%
Principal		$ 550,000,000			$ 0
EQM | EQM Senior notes
Debt Instrument [Line Items]
Net proceeds from offering	$ 2,465,800,000
Discount	11,800,000
Debt issuance costs	$ 22,400,000
EQM | EQM 4.75% Senior Notes due 2023 | EQM Senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)	4.75%
Principal	$ 1,100,000,000
EQM | EQM 5.50% Senior Notes due 2028 | EQM Senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)	5.50%
Principal	$ 850,000,000
EQM | EQM 6.50% Senior Notes due 2048 | EQM Senior notes
Debt Instrument [Line Items]
Interest rate (as a percent)	6.50%
Principal	$ 550,000,000
EQM | Line of credit | $2.5 Billion Senior Notes
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 2,500,000,000		$ 2,500,000,000	$ 2,500,000,000

Debt - EQM 4.125% and 4.00% Sen

Debt - EQM 4.125% and 4.00% Senior Notes (Details) - EQM Senior notes - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2014
EQM 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Interest rate (as a percent)	4.125%
Principal	$ 500,000	$ 500,000
EQM 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate (as a percent)	4.00%
Principal	$ 500,000	$ 500,000
EQM | EQM 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Interest rate (as a percent)	4.125%		4.125%
Principal			$ 500,000
EQM | EQM 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate (as a percent)	4.00%			4.00%
Principal				$ 500,000

Debt - RMP Credit Facility (Det

Debt - RMP Credit Facility (Details) - USD ($)	2 Months Ended	7 Months Ended
	Dec. 31, 2017	Jul. 23, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Letters of credit outstanding	$ 466,000,000		$ 641,500,000
Line of credit | RMP Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 850,000,000
Letters of credit outstanding	1,000,000
Maximum amount of short term loans outstanding	286,000,000	375,000,000
Average daily balance of short term loans outstanding	$ 268,000,000	$ 300,000,000
Weighted average annual interest rate (as a percent)	3.10%	3.80%

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income tax expense:
Federal	$ 41,788	$ 43,794	$ 94,068
State	16,108	10,239	21,751
Total current income tax expense	57,896	54,033	115,819
Deferred income tax expense (benefit):
Federal	96,499	148,623	(7,892)
State	(71,253)	9,746	(9,684)
Total deferred income tax expense (benefit)	25,246	158,369	(17,576)
Total income tax expense	$ 83,142	$ 212,402	$ 98,243

Income Taxes - Effective Tax Ra

Income Taxes - Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax expense at statutory rate	$ 124,828	$ 187,201	$ 169,860
Tax Reform Legislation	7,443	129,266	0
State income tax expense	21,827	12,710	7,844
Noncontrolling interests' share of earnings	(61,505)	(116,539)	(112,672)
Impairment of goodwill	16,535	0	0
Rice Midstream Holdings income not subject to tax	(26,538)	(13,460)	0
Regulatory (asset) liability	(368)	10,488	35,438
Other	920	2,736	(2,227)
Total income tax expense	$ 83,142	$ 212,402	$ 98,243
Effective tax rate	14.00%	39.70%	20.20%

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 01, 2018
Income Taxes [Line Items]
Tax Cuts and Jobs Act, deferred tax asset, income tax expense	$ 7,500	$ 129,300
Tax expense from regulated liability (asset)	$ 368	$ (10,488)	$ (35,438)
Strike Force Midstream
Income Taxes [Line Items]
Limited partner ownership interest (as a percent)	25.00%
Strike Force Midstream | RMP and Gulfport Midstream
Income Taxes [Line Items]
Limited partner ownership interest (as a percent)				25.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Total deferred income tax asset:
Net operating loss carryforwards	$ 36,202	$ 0
Investment in partnerships	559,858	257,128
Other	1,261	0
Total excluding valuation allowance	597,321	257,128
Valuation allowance	0	0
Total net deferred income tax asset	$ 597,321	$ 257,128

Concentrations of Credit Risk (

Concentrations of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues | Customer Concentration Risk | EQT Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	74.00%	74.00%	75.00%
Revenues | Customer Concentration Risk | PNG Companies, LLC
Concentration Risk [Line Items]
Concentration risk, percentage	7.00%	11.00%	12.00%
Accounts receivable | Credit Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	51.00%	39.00%

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)$ / gal	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Long-term Purchase Commitment [Line Items]
Remedial action included in other credits	$ 2.1
Operating lease rentals	7.2	$ 5.4	$ 4.7
Future lease payments due, total	68.4
Future lease payments due, 2019	7.2
Future lease payments due, 2020	6.3
Future lease payments due, 2021	6.2
Future lease payments due, 2022	6.2
Future lease payments due, 2023	6
Future lease payments due, 2024 and thereafter	$ 36.5
Surcharge entitled to per 1,000 gallons of water sold (in dollars per gallon) | $ / gal	3.50
Supply commitment, funded expenditure	$ 13.4	$ 11.7
Amount authorized under supply commitment	0.8
Capital Addition Purchase Commitments
Long-term Purchase Commitment [Line Items]
Expenditures authorized	$ 29.5

Post-retirement Benefit Plans (

Post-retirement Benefit Plans (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Settlement charge to retirement plan		$ 5.2
Regulatory asset, amortization period			16 years
Reimbursed funding of Retirement plan					$ 1.9
Defined benefit pension expense					0.1
Defined contribution plan expense	$ 0.6
Post-retirement plan expense, excluding pension			$ 1.2	$ 1.2	$ 1.2

Interim Financial Information_3

Interim Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Nov. 13, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Effect of Fourth Quarter Events [Line Items]
Impairment of goodwill										$ 261,941		$ 0		$ 0
Total operating revenues		$ 384,791	$ 364,584	$ 374,697	$ 371,026	$ 292,378	$ 206,293	$ 196,815	$ 200,072	1,495,098	[1]	895,558	[1]	732,272	[1]
Total operating income		(59,446)	218,322	234,868	249,340	118,494	141,282	139,178	144,096	643,084		543,050		465,066
Net income (loss)		(118,040)	185,966	219,607	223,744	(27,861)	115,451	115,885	118,982	511,277		322,457		387,073
Net income (loss) attributable to Equitrans Midstream		$ (48,223)	$ 82,825	$ 101,067	$ 82,729	$ (127,125)	$ 33,334	$ 34,366	$ 32,269	$ 218,398		$ (27,156)		$ 65,153
Basic:
Weighted average common stock outstanding (in shares)		254,432	254,432	254,432	254,432	254,432	254,432	254,432	254,432	254,432		254,432		254,432
Net income (loss) (in dollars per share)		$ (0.19)	$ 0.33	$ 0.40	$ 0.33	$ (0.50)	$ 0.13	$ 0.14	$ 0.13	$ 0.86		$ (0.11)		$ 0.26
Diluted:
Weighted average common stock outstanding (in shares)		254,432	255,033	255,033	255,033	254,432	255,033	255,033	255,033	255,033		254,432		255,033
Net income (loss) (in dollars per share)		$ (0.19)	$ 0.32	$ 0.40	$ 0.32	$ (0.50)	$ 0.13	$ 0.13	$ 0.13	$ 0.86		$ (0.11)		$ 0.26
RMP
Effect of Fourth Quarter Events [Line Items]
Impairment of goodwill	$ 261,941	$ 261,900
[1]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of approximately $1.1 billion, $665.9 million and $551.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. See Note 8.

Consolidated Variable Interes_3

Consolidated Variable Interest Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Operating revenues	$ 1,495,098	$ 826,522	$ 732,272
Operating expenses	768,445	245,032	204,416
Other (expenses) income	(55,305)	(9,586)	10,098
Net income	671,348	571,904	537,954
Net cash provided by operating activities	1,187,239	650,550	537,904
Net cash used in investing activities	(2,950,254)	(456,968)	(732,033)
Net cash provided by (used in) financing activities	1,725,930	(251,393)	$ (106,459)
Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	17,515	2,557
Accounts receivable
Variable Interest Entity [Line Items]
Assets	254,390	132,108
Other current assets
Variable Interest Entity [Line Items]
Assets	14,909	12,662
Net property, plant and equipment
Variable Interest Entity [Line Items]
Assets	5,806,628	2,804,059
Investment in unconsolidated entity
Variable Interest Entity [Line Items]
Assets	1,510,289	460,546
Goodwill
Variable Interest Entity [Line Items]
Assets	1,123,813	0
Net intangible assets
Variable Interest Entity [Line Items]
Assets	576,113	0
Other assets
Variable Interest Entity [Line Items]
Assets	152,464	136,895
Accounts payable
Variable Interest Entity [Line Items]
Liabilities	207,877	78,713
Capital contribution payable to the MVP Joint Venture
Variable Interest Entity [Line Items]
Liabilities	169,202	105,734
Accrued interest
Variable Interest Entity [Line Items]
Liabilities	80,199	10,926
Accrued liabilities
Variable Interest Entity [Line Items]
Liabilities	20,672	16,871
Credit facility borrowings
Variable Interest Entity [Line Items]
Liabilities	625,000	180,000
EQM Senior notes
Variable Interest Entity [Line Items]
Liabilities	3,456,639	987,352
Regulatory and other long-term liabilities
Variable Interest Entity [Line Items]
Liabilities	38,724	20,273
Affiliated Entity | Accounts receivable
Variable Interest Entity [Line Items]
Assets	174,800	103,300
Affiliated Entity | Accounts payable
Variable Interest Entity [Line Items]
Liabilities	$ 34,000	$ 31,700

Subsequent Events (Details)

Subsequent Events (Details) - USD ($)	Feb. 13, 2019	Jan. 10, 2019	Jan. 02, 2019	Dec. 31, 2018	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2018
Unit Purchase Agreements
Subsequent Event [Line Items]
Aggregate purchase price				$ 291,200,000
IDR Merger Agreement | Subsequent Event
Subsequent Event [Line Items]
Convertible units (in shares)	$ 2,500,000
Convertible units (in shares)	2,500,000
Convertible units (in shares)	$ 2,000,000
IDR Merger Agreement | EQM | Subsequent Event
Subsequent Event [Line Items]
Common units issued (in shares)	80,000,000
EQGP | Unit Purchase Agreements
Subsequent Event [Line Items]
Number of units purchased (in shares)						14,560,281
EQGP | Unit Purchase Agreements | Subsequent Event
Subsequent Event [Line Items]
Number of units purchased (in shares)					804,140
Aggregate purchase price			$ 16,100,000
EQGP | Limited Call Right | Subsequent Event
Subsequent Event [Line Items]
Number of units purchased (in shares)		11,097,287
Aggregate purchase price		$ 221,900,000
Limited Partner Common | EQGP
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)				290,569,047		290,569,047	290,569,047
Limited partner ownership interest (as a percent)				96.10%
Limited Partner Common | EQM
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)				15,433,812		15,433,812	15,433,812
Limited partner ownership interest (as a percent)							12.70%
Limited Partner Common | EQM | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	117,245,455
Limited partner ownership interest (as a percent)	59.90%
Limited Partner Common | EQM | EQGP
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)				21,811,643		21,811,643	21,811,643
Limited partner ownership interest (as a percent)							17.90%
Limited Partner Common | EQM | Equitrans Gathering Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	89,505,616
Limited Partner Common | EQM | EQM GP Corporation | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	89,536
Limited Partner Common | EQM | Equitrans Midstream Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	27,650,303
Limited Partner Common | EQM | Equitrans Gathering Holdings, EQM GP Corporation, And Equitrans Midstream Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Limited partner ownership interest (as a percent)	56.50%
Phantom Units | EQGP | Subsequent Event
Subsequent Event [Line Items]
Number of shares granted (in shares)		29,829
Common Class B | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	7,000,000
Common Class B | IDR Merger Agreement | EQM | Subsequent Event
Subsequent Event [Line Items]
Common units issued (in shares)	7,000,000
Common Class B | Limited Partner Common | EQM | Subsequent Event
Subsequent Event [Line Items]
Limited partner ownership interest (as a percent)	3.40%
Common Class B | Limited Partner Common | EQM | Equitrans Gathering Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	6,153,907
Common Class B | Limited Partner Common | EQM | EQM GP Corporation | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	6,155
Common Class B | Limited Partner Common | EQM | Equitrans Midstream Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Partners' capital common units outstanding (in shares)	839,938