EQM Midstream Partners 10-Q 30 Jul 19 2019 Q2 Quarterly report Financial data

Cover

Cover	6 Months Ended
	Jun. 30, 2019shares
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-35574
Entity Registrant Name	EQM Midstream Partners, LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	37-1661577
Entity Address, Address Line One	625 Liberty Avenue, Suite 2000
Entity Address, City or Town	Pittsburgh
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15222
City Area Code	412
Local Phone Number	395-2688
Title of 12(b) Security	Common Units Representing Limited Partner Interests
Trading Symbol	EQM
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Small Business Entity	false
Entity Shell Company	false
Entity Common Units, Unit Outstanding	200,457,630
Entity Central Index Key	0001540947
Amendment Flag	false
Current Fiscal Year End	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Class B Units
Document Information [Line Items]
Entity Common Units, Unit Outstanding	7,000,000

Statements of Consolidated Oper

Statements of Consolidated Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018
Income Statement [Abstract]
Operating revenues	[1],[2]	$ 406,167	$ 374,697	$ 795,949		$ 745,723
Operating expenses:
Operating and maintenance	[1],[3]	46,556	43,270	74,439		70,442
Selling, general and administrative	[1],[3]	26,406	27,712	59,326		54,102
Separation and other transaction costs	[1]	15,358	5,350	18,871		5,350
Depreciation	[1]	56,515	42,110	103,580	[4]	83,390	[4]
Amortization of intangible assets	[1]	13,750	10,387	24,137	[4]	20,773	[4]
Impairment of long-lived assets	[1],[5]	80,135	0	80,135	[4]	0	[4]
Total operating expenses	[1]	238,720	128,829	360,488		234,057
Operating income	[1]	167,447	245,868	435,461		511,666
Equity income	[1],[6]	36,782	10,938	67,845	[4]	19,749	[4]
Other income	[1]	1,959	944	4,169		1,848
Net interest expense	[1],[7]	49,717	23,065	99,073		35,735
Net income	[1],[4]	156,471	234,685	408,402		497,528
Net income attributable to noncontrolling interests	[1]	4,033	853	4,033		3,346
Net income attributable to EQM	[1]	152,438	233,832	404,369		494,182
Calculation of limited partner common unit interest in net income:
Net income attributable to EQM	[1]	152,438	233,832	404,369		494,182
Less: Series A Preferred Units interest in net income	[1]	(22,979)	0	(22,979)		0
Less: pre-acquisition net income allocated to EQT	[1]	0	(72,620)	0		(155,752)
Less: general partner interest in net income – general partner units	[1]	0	(1,700)	0		(4,791)
Less: general partner interest in net income – IDRs	[1]	0	(68,121)	0		(112,285)
Limited partner interest in net income	[1]	$ 129,459	$ 91,391	$ 381,390		$ 221,354
Net income per limited partner common unit – basic (in dollars per share)	[1],[8]	$ 0.65	$ 1.09	$ 2.15		$ 2.69
Net income per limited partner common unit – diluted (in dollars per share)	[1],[8]	$ 0.62	$ 1.09	$ 2.07		$ 2.69
Weighted average limited partner common units outstanding – basic (in shares)	[1]	200,482	83,553	177,498		82,290
Weighted average limited partner common units outstanding – diluted (in shares)	[1]	207,482	83,553	195,645		82,290
Cash distributions declared per unit (in dollars per share)	[1],[9]	$ 1.160	$ 1.09	$ 2.305		$ 2.155
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of $284.0 million and $285.3 million for the three months ended June 30, 2019 and 2018 , respectively, and $568.5 million and $550.9 million for the six months ended June 30, 2019 , respectively. See Note 8 .
[3]	For the three and six months ended June 30, 2019 , operating and maintenance expense included $15.2 million and $26.2 million of charges from Equitrans Midstream Corporation (Equitrans Midstream), respectively. For the three and six months ended June 30, 2018 , operating and maintenance expense included charges from EQT of $12.3 million and $24.4 million , respectively. For the three and six months ended June 30, 2019 , selling, general and administrative expense included charges from Equitrans Midstream of $23.5 million and $51.4 million , respectively. For the three and six months ended June 30, 2018 , selling, general and administrative expense included charges from EQT of $25.6 million and $49.4 million , respectively. See Note 8 .
[4]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.
[5]	See Note 3 for disclosure regarding impairment of certain of EQM's long-lived assets.
[6]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 9 .
[7]	Net interest expense included interest income on the Preferred Interest in EQT Energy Supply, LLC (EES) of $1.6 million and $1.7 million for the three months ended June 30, 2019 and 2018 , respectively, and $3.2 million and $3.3 million for the six months ended June 30, 2019 and 2018 , respectively.
[8]	See Note 12 for further disclosure on EQM's calculation of net income per limited partner unit (basic and diluted).
[9]	Represents the cash distributions declared related to the period presented. See Note 12 .

Statements of Consolidated Op_2

Statements of Consolidated Operations (Unaudited) (Parenthetical) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating and maintenance	[1],[2]	$ 46,556	$ 43,270	$ 74,439	$ 70,442
Selling, general and administrative expenses	[1],[2]	26,406	27,712	59,326	54,102
EQT
Operating revenues		284,000	285,300	568,500	550,900
Operating and maintenance			12,300		24,400
Selling, general and administrative expenses			25,600		49,400
EES
Interest income		1,600	$ 1,700	3,200	$ 3,300
ETRN
Operating and maintenance		15,200		26,200
Selling, general and administrative expenses		$ 23,500		$ 51,400
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	For the three and six months ended June 30, 2019 , operating and maintenance expense included $15.2 million and $26.2 million of charges from Equitrans Midstream Corporation (Equitrans Midstream), respectively. For the three and six months ended June 30, 2018 , operating and maintenance expense included charges from EQT of $12.3 million and $24.4 million , respectively. For the three and six months ended June 30, 2019 , selling, general and administrative expense included charges from Equitrans Midstream of $23.5 million and $51.4 million , respectively. For the three and six months ended June 30, 2018 , selling, general and administrative expense included charges from EQT of $25.6 million and $49.4 million , respectively. See Note 8 .

Statements of Consolidated Cash

Statements of Consolidated Cash Flows (Unaudited) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	[1],[2]	$ 408,402	$ 497,528
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	[1],[2]	103,580	83,390
Amortization of intangible assets	[1],[2]	24,137	20,773
Impairment of long-lived assets	[1],[2],[3]	80,135	0
Equity income	[1],[2],[4]	(67,845)	(19,749)
AFUDC – equity	[2]	(4,453)	(2,137)
Non-cash long-term compensation expense	[2]	255	639
Changes in other assets and liabilities:
Accounts receivable	[2]	(3,583)	3,947
Accounts payable	[2]	(23,231)	39,728
Other assets and other liabilities	[2]	(7,154)	(1,212)
Net cash provided by operating activities	[2]	510,243	622,907
Cash flows from investing activities:
Capital expenditures	[2]	(527,803)	(382,946)
Capital contributions to the MVP Joint Venture	[2]	(301,175)	(182,805)
Bolt-on Acquisition (defined in Note 2), net of cash acquired	[2]	(848,625)	0
Drop-Down Transaction	[5]	0	(1,193,160)
Principal payments received on the Preferred Interest	[2]	2,298	2,172
Net cash used in investing activities	[2]	(1,675,305)	(1,756,739)
Cash flows from financing activities:
Proceeds from credit facility borrowings	[2]	1,047,000	2,390,500
Payments on credit facility borrowings	[2]	(572,000)	(2,596,500)
Pay-down of long-term debt associated with Bolt-on Acquisition (Note 2)		(28,325)	0
Proceeds from issuance of long-term debt	[2]	0	2,500,000
Debt discount and issuance costs	[5]	0	(30,295)
Proceeds from issuance of Series A Preferred Units, net of offering costs		1,158,313	0
Distributions paid to common unitholders	[2]	(440,816)	(326,601)
Distributions paid to noncontrolling interest	[2]	0	(750)
Acquisition of 25% of Strike Force Midstream LLC	[2]	0	(175,000)
Capital contributions	[2]	0	15,672
Net contributions from EQT	[5]	0	3,660
Net cash provided by financing activities	[2]	1,164,172	1,780,686
Net change in cash and cash equivalents	[2]	(890)	646,854
Cash and cash equivalents at beginning of period	[2]	17,515	54,600
Cash and cash equivalents at end of period	[2]	16,625	701,454
Cash paid during the period for:
Interest, net of amount capitalized	[2]	106,001	33,621
Non-cash activity during the period for:
Increase (decrease) in capital contribution receivable from Equitrans Midstream/EQT	[2]	$ 497	$ (12,251)
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.
[3]	See Note 3 for disclosure regarding impairment of certain of EQM's long-lived assets.
[4]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 9 .
[5]	Accounts receivable as of June 30, 2019 and December 31, 2018 included approximately $126.7 million and $174.8 million , respectively, of related party accounts receivable from EQT.

Statements of Consolidated Ca_2

Statements of Consolidated Cash Flows (Unaudited) (Parenthetical)	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Percentage of voting interests acquired	25.00%

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents		$ 16,625	$ 17,515
Accounts receivable	[1]	274,790	254,390
Other current assets		21,971	14,909
Total current assets		313,386	286,814
Property, plant and equipment		8,158,272	6,367,530
Less: accumulated depreciation		(783,130)	(560,902)
Net property, plant and equipment	[1]	7,375,142	5,806,628
Investment in unconsolidated entity		2,066,330	1,510,289
Goodwill		1,237,456	1,123,813
Net intangible assets		868,965	576,113
Other assets		201,891	152,464
Total assets		12,063,170	9,456,121
Current liabilities:
Accounts payable	[2]	179,448	207,877
Due to Equitrans Midstream		76,863	44,509
Capital contribution payable to the MVP Joint Venture		356,223	169,202
Accrued interest		73,443	80,199
Accrued liabilities		38,265	20,672
Total current liabilities		724,242	522,459
Credit facility borrowings		1,372,500	625,000
Senior notes		3,459,323	3,456,639
Regulatory and other long-term liabilities		81,093	38,724
Total liabilities		5,637,158	4,642,822
Equity:
Series A Preferred Units		1,181,292	0
General partner		0	29,626
Noncontrolling interest	[3]	490,095	0
Total equity	[4]	6,426,012	4,813,299
Total liabilities and equity		12,063,170	9,456,121
Common Units
Equity:
Common and Class B		4,748,269	4,783,673
Class B Units
Equity:
Common and Class B		$ 6,356	$ 0
[1]	Accounts receivable as of June 30, 2019 and December 31, 2018 included approximately $126.7 million and $174.8 million , respectively, of related party accounts receivable from EQT.
[2]	Accounts payable as of December 31, 2018 included approximately $34.0 million of related party accounts payable to EQT. There was no related party balance with EQT included in accounts payable as of June 30, 2019 .
[3]	Noncontrolling interest as of June 30, 2019 represents third-party ownership in Eureka Midstream Holdings, LLC (Eureka Midstream). See Note 2 for further information.
[4]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts receivable, for doubtful accounts	$ 138	$ 75
Series A Preferred Units issued (in shares)	24,605,291	0
Series A Preferred Units outstanding (in shares)	24,605,291	0
General partner, units issued (in shares)	0	1,443,015
General partner, units outstanding (in shares)	0	1,443,015
Accounts receivable, related parties	$ 126,700	$ 174,800
Accounts payable, related parties		$ 34,000
Common Units
Common units issued (in shares)	200,457,630	120,457,638
Common units outstanding (in shares)	200,457,630	120,457,638
Class B Units
Common units issued (in shares)	7,000,000	0
Common units outstanding (in shares)	7,000,000	0

Statements of Consolidated Equi

Statements of Consolidated Equity (Unaudited) - USD ($) $ in Thousands		Total		General Partner	Predecessor Equity	Noncontrolling Interest	Series A Preferred UnitsLimited Partners	Common UnitsLimited Partners	Class B UnitsLimited Partners
Beginning balance at Dec. 31, 2017	[1]	$ 6,238,864		$ 1,252	$ 3,916,434	$ 173,472	$ 0	$ 2,147,706	$ 0
Increase (Decrease) in Partners' Capital
Net income	[1]	262,843		47,281	83,132	2,493		129,937
Capital contributions	[1]	2,799		50				2,749
Equity-based compensation plans	[1]	499			168			331
Distributions paid to unitholders	[1]	(158,735)		(43,294)	(32,845)			(82,596)
Net contributions from EQT	[1]	1,015			1,015
Distributions paid to noncontrolling interests	[1]	(750)				(750)
Ending balance at Mar. 31, 2018	[1]	6,346,535		5,289	3,967,904	175,215	0	2,198,127	0
Beginning balance at Dec. 31, 2017	[1]	6,238,864		1,252	3,916,434	173,472	0	2,147,706	0
Increase (Decrease) in Partners' Capital
Net income	[1],[2]	497,528
Ending balance at Jun. 30, 2018	[1]	5,048,601		28,603	2,571,467	0	0	2,448,531	0
Beginning balance at Mar. 31, 2018	[1]	6,346,535		5,289	3,967,904	175,215	0	2,198,127	0
Increase (Decrease) in Partners' Capital
Net income	[1]	234,685	[2]	69,795	72,620	853		91,417
Acquisition of 25% of Strike Force Midstream LLC	[1]	(175,000)				(176,068)		1,068
Drop-Down Transaction	[1]	(1,193,160)			(1,436,297)			243,137
Capital contributions	[1]	622		10				612
Equity-based compensation plans	[1]	140			140
Distributions paid to unitholders	[1]	(167,866)		(46,491)	(35,545)			(85,830)
Net contributions from EQT	[1]	2,645			2,645
Ending balance at Jun. 30, 2018	[1]	5,048,601		28,603	$ 2,571,467	0	0	2,448,531	0
Beginning balance at Dec. 31, 2018	[1]	4,813,299		29,626		0	0	4,783,673	0
Increase (Decrease) in Partners' Capital
Net income	[1]	251,931		1,767				246,699	3,465
Equity-based compensation plans	[1]	255						255
Distributions paid to unitholders	[1]	(211,292)		(75,175)				(136,117)
Equity restructuring associated with the EQM IDR Transaction	[1]			43,782				(42,305)	(1,477)
Ending balance at Mar. 31, 2019	[1]	4,854,193		0		0	0	4,852,205	1,988
Beginning balance at Dec. 31, 2018	[1]	4,813,299		29,626		0	0	4,783,673	0
Increase (Decrease) in Partners' Capital
Net income	[1],[2]	408,402
Ending balance at Jun. 30, 2019	[1]	6,426,012		0		490,095	1,181,292	4,748,269	6,356
Beginning balance at Mar. 31, 2019	[1]	4,854,193		0		0	0	4,852,205	1,988
Increase (Decrease) in Partners' Capital
Net income	[1]	156,471	[2]			4,033	22,979	125,091	4,368
Capital contributions	[1]	497						497
Distributions paid to unitholders	[1]	(229,524)						(229,524)
Issuance of Series A Preferred Units, net of offering costs	[1]	1,158,313					1,158,313
Bolt-on Acquisition	[1]	486,062				486,062
Ending balance at Jun. 30, 2019	[1]	$ 6,426,012		$ 0		$ 490,095	$ 1,181,292	$ 4,748,269	$ 6,356
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.
[2]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.

Statements of Consolidated Eq_2

Statements of Consolidated Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Distributions paid to unitholders (dollars per common unit)	$ 1.145	$ 1.13	$ 1.065	$ 1.025

Financial Statements

Financial Statements	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Financial Statements	Financial Statements Organization EQM is a growth-oriented Delaware limited partnership formed by EQT in January 2012. Prior to the completion of the EQM IDR Transaction (defined below), EQM Midstream Services, LLC was the general partner of EQM (the Former EQM General Partner). Following the consummation of the EQM IDR Transaction, EQGP Services, LLC, a wholly-owned indirect subsidiary of Equitrans Midstream, became the general partner of EQM (the New EQM General Partner). References in these consolidated financial statements to Equitrans Midstream refer collectively to Equitrans Midstream Corporation and its consolidated subsidiaries. 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 operations 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). On November 12, 2018, the Separation was effected through a series of transactions that culminated in EQT's contribution of the Midstream Business to Equitrans Midstream. On February 22, 2019, Equitrans Midstream completed its previously announced simplification transaction pursuant to that certain Agreement and Plan of Merger, dated as of February 13, 2019 (the IDR Merger Agreement), by and among Equitrans Midstream, EQM, the Former EQM General Partner, EQGP, the New EQM General Partner, Equitrans Merger Sub, LP, a Delaware limited partnership (Merger Sub), and certain other parties thereto. Pursuant to the IDR Merger Agreement, on February 22, 2019, (i) Merger Sub merged with and into EQGP (the Merger) with EQGP continuing as the surviving limited partnership and a wholly-owned subsidiary of EQM following the Merger, and (ii) each of (a) the incentive distribution rights (IDRs) in EQM, (b) the economic portion of the general partner interest in EQM and (c) the issued and outstanding common units representing limited partner interests in EQGP were canceled, and, as consideration for such cancellation, certain affiliates of Equitrans Midstream received on a pro rata basis 80,000,000 newly-issued EQM common units and 7,000,000 newly-issued Class B units (Class B units), both representing limited partner interests in EQM, and the New EQM General Partner retained the non-economic general partner interest in EQM (the EQM IDR Transaction). Additionally, as part of the EQM IDR Transaction, the 21,811,643 EQM common units held by EQGP were canceled and 21,811,643 EQM common units were issued pro rata to certain affiliates of Equitrans Midstream. See Note 5 for further information on the EQM IDR Transaction and Class B Units. The EQM IDR Transaction constituted an exchange of equity interests between entities under common control and not a transfer of a business. Therefore, the exchange resulted in a reclassification, as of February 22, 2019, of a $43.8 million deficit capital balance from the general partner line item to the common and Class B line items in EQM's consolidated balance sheets based on the respective limited partner ownership interests. The reclassification represented an allocation of the carrying value of the exchanged general partner interest. Prior to the EQM IDR Transaction, when distributions related to the general partner interest and IDRs were made, earnings equal to the amount of distributions were allocated to the general partner before the remaining earnings were allocated to the limited partner unitholders based on their respective ownership percentages. Subsequent to the EQM IDR Transaction, no earnings will be allocated to the general partner. The allocation of net income attributable to EQM for purposes of calculating net income per limited partner unit is described in Note 12 . On March 13, 2019, EQM entered into a Convertible Preferred Unit Purchase Agreement (inclusive of certain Joinder Agreements entered into on March 18, 2019, the Preferred Unit Purchase Agreement) with certain investors to issue and sell in a private placement (the Private Placement) an aggregate of 24,605,291 Series A Perpetual Convertible Preferred Units (Series A Preferred Units) representing limited partner interests in EQM for a cash purchase price of $48.77 per Series A Preferred Unit, resulting in total gross proceeds of approximately $1.2 billion . The net proceeds from the Private Placement were used in part to fund the purchase price in the Bolt-on Acquisition (defined in Note 2 ) and to pay certain fees and expenses related to the Bolt-on Acquisition, and the remainder was used for general partnership purposes. The Private Placement closed concurrently with the closing of the Bolt-on Acquisition on April 10, 2019 . See Note 5 for further information on the Series A Preferred Units and the Bolt-on Acquisition. Following the EQM IDR Transaction and the closing of the Private Placement, and as of June 30, 2019 , Equitrans Midstream held a 53.5% limited partner interest (after taking into account the Series A Preferred Units issued in the Private Placement on an as-converted basis) and the non-economic general partner interest in EQM. See Note 5 for further information on the EQM IDR Transaction and Private Placement. Basis of Presentation EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions represented business combinations between entities under common control. The recast is for the period the acquired businesses were under the common control of EQT, which began on November 13, 2017 as a result of EQT's acquisition of Rice Energy Inc. (Rice) (the Rice Merger). EQM recorded the assets and liabilities acquired in the Drop-Down Transaction and the EQM-RMP Merger at their carrying amounts to EQT on the effective dates of the transactions. The consolidated financial statements are not necessarily indicative of the actual results of operations if EQM and the assets acquired in the Drop-Down Transaction and the EQM-RMP Merger had been operated together during the pre-acquisition periods. Following the completion of the Bolt-on Acquisition, EQM evaluated Eureka Midstream for consolidation and determined that Eureka Midstream does not meet the criteria for variable interest entity classification due to its ability to independently finance its operations through the Eureka Credit Facility (as defined in Note 10 ), as well as each member having proportional voting rights through their equity investments. As such, as of June 30, 2019 , EQM consolidates Eureka Midstream using the voting interest model, recording noncontrolling interest related to the third-party ownership interests in Eureka Midstream. The accompanying unaudited consolidated financial statements have been prepared in accordance with GAAP for interim financial information and with the requirements of Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these unaudited consolidated financial statements include all adjustments (consisting of only normal recurring adjustments, unless otherwise disclosed in this Form 10-Q) necessary for a fair presentation of the financial position of EQM as of June 30, 2019 and December 31, 2018 , the results of its operations and equity for the three and six months ended June 30, 2019 and 2018 , and its cash flows for the six months ended June 30, 2019 and 2018 . The balance sheet at December 31, 2018 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by GAAP for complete financial statements. Due to the seasonal nature of EQM's utility customer contracts, the interim statements for the three and six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 . EQM does not have any employees. Operational, management and other services for EQM are provided by the directors and officers of the New EQM General Partner and employees of Equitrans Midstream. For further information, refer to the consolidated financial statements and related footnotes for the year ended December 31, 2018, as well as "Management's Discussion and Analysis of Financial Condition and Results of Operations" contained therein. Recently Issued Accounting Standards In February 2016, the FASB issued ASU 2016-02, Leases . The standard requires entities to record assets and obligations for contracts currently recognized as operating leases. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements . The update provides an optional transition method of adoption that permits entities 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. Under the optional transition method, comparative financial information and disclosures are not required. The update also provides transition practical expedients. The standard requires disclosures of the nature, maturity and value of an entity's lease liabilities and elections taken by the entity. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842): Codification Improvements , which, among other things, clarifies interim disclosure requirements in the year of ASU 2016-02 adoption. EQM adopted ASU 2016-02, ASU 2018-11 and ASU 2019-01 on January 1, 2019 using the optional transition method. EQM uses a lease accounting system to monitor its current population of lease contracts. EQM implemented 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. For the disclosures required by the standards, see Note 4 . In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments. The standard amends guidance on reporting credit losses for 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 in current GAAP, and, in its place, requires an entity to recognize its 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. EQM is currently evaluating the effect this standard will have 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. EQM 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. EQM early-adopted the standard using the prospective method of adoption on January 1, 2019. Following the adoption of ASU 2018-15, EQM began capitalizing certain implementation costs related to cloud computing arrangements that are service contracts. The capitalized portion of these costs are included in the property, plant and equipment line on the consolidated balance sheets and will be amortized over the term of EQM's hosting arrangement, which has a fixed term of seven years . For the three and six months ended June 30, 2019 , EQM did no t recognize any amortization expense related to implementation costs on its cloud computing arrangements as such assets were not in use. The costs will be included in the selling, general and administrative expense line on the accompanying statements of consolidated operations when recognized. In August 2018, the U.S. Securities and Exchange Commission (SEC) adopted a final rule under SEC Release No. 33-10532, Disclosure Update and Simplification

Acquisitions and Mergers

Acquisitions and Mergers	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Acquisitions and Mergers	Acquisitions and Mergers Bolt-on Acquisition On March 13, 2019, EQM entered into a Purchase and Sale Agreement (the Purchase and Sale Agreement) with North Haven Infrastructure Partners II Buffalo Holdings, LLC (NHIP), an affiliate of Morgan Stanley Infrastructure Partners, pursuant to which EQM acquired from NHIP a 60% Class A interest in Eureka Midstream Holdings, LLC (Eureka Midstream) and a 100% interest in Hornet Midstream Holdings, LLC (Hornet Midstream) (collectively, the Bolt-on Acquisition) for total consideration of approximately $1.03 billion , composed of approximately $864 million in cash and approximately $167 million in assumed pro-rata debt, subject to certain adjustments set forth in the Purchase and Sale Agreement. Eureka Midstream owns a 190 -mile gathering header pipeline system in Ohio and West Virginia that services both dry Utica and wet Marcellus Shale production. Hornet Midstream owns a 15 -mile, high-pressure gathering system in West Virginia that connects to the Eureka Midstream system. The Bolt-on Acquisition closed on April 10, 2019 and was funded through proceeds from the Private Placement that closed concurrently with the Bolt-on Acquisition. See Notes 1 and 5 for further information on the Private Placement. On the closing of the Bolt-on Acquisition, a subsidiary of Hornet Midstream terminated all of its obligations under its term loan credit agreement and repaid the $28.2 million outstanding principal balance and $0.1 million in related interest and fees. EQM recorded $15.2 million and $16.7 million in acquisition-related expenses related to the Bolt-on Acquisition during the three and six months ended June 30, 2019 , respectively. The Bolt-on Acquisition acquisition-related expenses included $13.5 million for professional fees and $1.7 million for compensation arrangements for the three months ended June 30, 2019 and $15.0 million for professional fees and $1.7 million for compensation arrangements for the six months ended June 30, 2019 and are included in separation and other transaction costs in the statements of consolidated operations. Allocation of Purchase Price. The Bolt-on Acquisition was accounted for as a business combination using the acquisition method. The following table summarizes the preliminary purchase price and preliminary estimated fair values of assets and liabilities assumed as of April 10, 2019, with any excess of purchase price over estimated fair value of the identified net assets acquired recorded as goodwill. The $113.6 million of goodwill has been allocated to the Gathering segment. Such goodwill primarily relates to additional commercial opportunities, a diversified producer customer mix, increased exposure to dry Utica and wet Marcellus acreage and operating leverage within the Gathering segment. The purchase price remains subject to post-closing purchase price adjustments; thus, the purchase price adjustments included in the financial statements are preliminary as of June 30, 2019 . EQM expects to complete the purchase price allocation once EQM has received all of the necessary information, at which time the value of the assets and liabilities will be revised as appropriate. The following table summarizes the preliminary allocation of the fair value of the assets and liabilities of the Bolt-on Acquisition as of April 10, 2019 by EQM. (in thousands) Preliminary Purchase Price Allocation Consideration given: Cash consideration $ 861,250 Buyout of Eureka Midstream Class B Units and incentive compensation 2,530 Total consideration 863,780 Fair value of liabilities assumed: Current liabilities 52,458 Long-term debt 300,825 Other long-term liabilities 10,203 Amount attributable to liabilities assumed 363,486 Fair value of assets acquired: Cash 15,145 Accounts receivable 16,817 Inventory 12,991 Other current assets 882 Net property, plant and equipment 1,222,284 Intangible assets 317,000 Other assets 14,567 Amount attributable to assets acquired 1,599,686 Noncontrolling interest (486,062 ) Goodwill $ 113,642 The estimated fair value of midstream facilities and equipment, generally consisting of pipeline systems and compression stations, were estimated using the cost approach. Significant unobservable inputs in the estimate of fair value include management's assumptions about the replacement costs for similar assets, the relative age of the acquired assets and any potential economic or functional obsolescence associated with the acquired assets. As a result, the estimated fair value of the midstream facilities and equipment represent a Level 3 fair value measurement. The non-controlling interest in Eureka Midstream is estimated to be $486.1 million . The fair value of the noncontrolling interest was calculated based on the enterprise value of Eureka Midstream and the percentage ownership not acquired by EQM. Significant unobservable inputs in the enterprise value of Eureka Midstream include the future revenue estimates and future cost assumptions, which remain subject to future refinement. As a result, the fair value measurement is based on significant inputs that are not observable in the market and thus represents a Level 3 fair value measurement. As part of the preliminary purchase price allocation, EQM identified intangible assets for customer relationships with third-party customers. The fair value of the customer relationships with third-party customers was determined using the income approach, which requires a forecast of the expected future cash flows generated and an estimated market-based weighted average cost of capital. Significant unobservable inputs in the determination of fair value include future revenue estimates, future cost assumptions and estimated customer retention rates. As a result, the estimated fair value of the identified intangible assets represents a Level 3 fair value measurement. Differences between the preliminary purchase price allocation and the final purchase price allocation may change the amount of intangible assets and goodwill ultimately recognized in conjunction with the Bolt-on Acquisition. EQM calculates amortization of intangible assets using the straight-line method over the estimated useful life of the intangible assets which is 20 years . Amortization expense recorded in the consolidated statements of operations for the three and six months ended June 30, 2019 was $3.4 million . The estimated annual amortization expense over the next five years is as follows: 2019 $8.1 million , 2020 $15.8 million , 2021 $15.8 million , 2022 $15.8 million and 2023 $15.8 million . Intangible assets, net as of June 30, 2019 are detailed below. (in thousands) As of June 30, 2019 Intangible assets 317,000 Less: accumulated amortization 3,375 Intangible assets, net $ 313,625 Post-Acquisition Operating Results. Subsequent to the completion of the Bolt-on Acquisition, Eureka Midstream and Hornet Midstream collectively contributed the following to both the Gathering segment and EQM's consolidated operating results for the period from April 10, 2019 through June 30, 2019 . (in thousands)(unaudited) April 10, 2019 through June 30, 2019 Operating revenues $ 28,928 Operating income attributable to EQM $ 12,496 Net income attributable to noncontrolling interests $ 4,033 Net income attributable to EQM $ 6,506 Unaudited Pro Forma Information. The following unaudited pro forma combined financial information presents EQM's results as though the EQM IDR Transaction and Bolt-on Acquisition had been completed at January 1, 2018. The pro forma combined financial information has been included for comparative purposes and is not necessarily indicative of the results that might have actually occurred had the EQM IDR Transaction and Bolt-on Acquisition taken place on January 1, 2018; furthermore, the financial information is not intended to be a projection of future results. (in thousands, except per unit data)(unaudited) Three Months Ended March 31, 2019 Pro forma operating revenues $ 421,362 Pro forma net income $ 264,215 Pro forma net income attributable to noncontrolling interests $ 3,205 Pro forma net income attributable to EQM $ 261,010 Pro forma income per unit (basic) $ 1.17 Pro forma income per unit (diluted) $ 1.12 (in thousands, except per unit data)(unaudited) Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Pro forma operating revenues $ 406,920 $ 803,945 Pro forma net income $ 242,587 $ 509,403 Pro forma net income attributable to noncontrolling interests $ 4,303 $ 8,710 Pro forma net income attributable to EQM $ 238,284 $ 500,693 Pro forma income per unit (basic) $ 1.06 $ 2.24 Pro forma income per unit (diluted) $ 1.03 $ 2.16 Shared Assets Transaction On March 31, 2019, EQM entered into an Assignment and Bill of Sale (the Assignment and Bill of Sale) with Equitrans Midstream pursuant to which EQM acquired certain assets and assumed certain leases that primarily support EQM’s operations for an aggregate cash purchase price of $49.7 million (the initial purchase price), which reflected the net book value of in-service assets and expenditures made for assets not yet in-service (collectively, and inclusive of the additional assets subsequently acquired as described in the following sentences, the Shared Assets Transaction). Further, pursuant to the Assignment and Bill of Sale, EQM acquired, effective on the first day of the second quarter of 2019, certain additional assets from Equitrans Midstream for $8.9 million cash consideration (the subsequent purchase price), reflecting the net book value of in-service assets and expenditures made in respect of assets not yet in-service as of June 30, 2019 , which subsequent purchase price is subject to certain adjustments. EQM may, pursuant to the Assignment and Bill of Sale, acquire certain additional assets from Equitrans Midstream for additional cash consideration reflecting the net book value of in-service assets and expenditures made with respect to assets not yet in-service and/or may assume an additional facilities lease. The initial and subsequent purchase prices were funded utilizing EQM’s $3 Billion Facility (defined in Note 10 ). Prior to the Shared Assets Transaction, EQM made quarterly payments to Equitrans Midstream based on fees allocated from Equitrans Midstream for use of in-service assets transferred to EQM in the Shared Assets Transaction. In connection with the entry into the Assignment and Bill of Sale, that certain omnibus agreement (ETRN Omnibus Agreement) among Equitrans Midstream, EQM and the New EQM General Partner (as successor to the Former EQM General Partner) was amended and restated in order to, among other things, govern Equitrans Midstream’s use of the acquired assets following their conveyance to EQM and provide for reimbursement of EQM by Equitrans Midstream for expenses incurred by EQM in connection with such use. EQM-RMP Merger On April 25, 2018, EQM entered into an Agreement and Plan of Merger (the Merger Agreement) with RMP, Rice Midstream Management LLC, the general partner of RMP (the RMP General Partner), the Former EQM General Partner, EQM Acquisition Sub, LLC, a wholly-owned subsidiary of EQM (Merger Sub), EQM GP Acquisition Sub, LLC, a wholly-owned subsidiary of EQM (GP Merger Sub), and, solely for certain limited purposes set forth therein, EQT. Pursuant to the Merger Agreement, on July 23, 2018, Merger Sub and GP Merger Sub merged with and into RMP and the RMP General Partner, respectively, with RMP and the RMP General Partner surviving as wholly-owned subsidiaries of EQM. Pursuant to the Merger Agreement, each RMP common unit issued and outstanding immediately prior to the effective time of the EQM-RMP Merger was converted into the right to receive 0.3319 EQM common units (the Merger Consideration), the issued and outstanding IDRs of RMP were canceled and each outstanding award of phantom units in respect of RMP common units fully vested and converted into the right to receive the Merger Consideration, less applicable tax withholding, in respect of each RMP common unit subject thereto. The aggregate Merger Consideration consisted of approximately 34 million EQM common units of which 9,544,530 EQM common units were received by an indirect wholly-owned subsidiary of EQT. As a result of the EQM-RMP Merger , RMP's common units are no longer publicly traded. Drop-Down Transaction On April 25, 2018, EQT, Rice Midstream Holdings LLC (Rice Midstream Holdings), a wholly-owned subsidiary of EQT, EQM and EQM Gathering Holdings, LLC (EQM Gathering), a wholly-owned subsidiary of EQM, entered into a Contribution and Sale Agreement pursuant to which EQM Gathering acquired from EQT all of EQT's interests in EQM Olympus, Strike Force and EQM WV in exchange for an aggregate of 5,889,282 EQM common units and aggregate cash consideration of approximately $1.15 billion . EQM Olympus owns a natural gas gathering system that gathers gas from wells located primarily in Belmont County, Ohio. Strike Force owns a 75% limited liability company interest in Strike Force Midstream LLC (Strike Force Midstream). The Drop-Down Transaction closed on May 22, 2018 with an effective date of May 1, 2018 . As a result of the recast associated with the EQM-RMP Merger and the Drop-Down Transaction, EQM recognized approximately $1,384.9 million of goodwill, all of which was allocated to two reporting units within the Gathering segment. The goodwill value was based on a valuation performed by EQT as of November 13, 2017 with regard to the Rice Merger. EQT recorded goodwill as the excess of the estimated enterprise value of RMP, EQM Olympus, Strike Force and EQM WV over the sum of the fair value amounts allocated to the assets and liabilities of RMP, EQM Olympus, Strike Force and EQM WV. Goodwill was attributed to additional growth opportunities, synergies and operating leverage within the Gathering segment. Prior to the recast, EQM had no goodwill. Following EQT's initial valuation, certain estimates used in the purchase price allocation were updated. The net impact of these measurement period adjustments increased goodwill by approximately $0.9 million . The purchase price allocation was finalized and the measurement period adjustments were recorded as current period adjustments. The following table summarizes the allocation of the fair value of the assets and liabilities of RMP, EQM Olympus, Strike Force and EQM WV as of November 13, 2017 through pushdown accounting from EQT, as well as certain measurement period adjustments made subsequent to EQT's initial valuation. Goodwill and Purchase Price Allocation (Thousands) Estimated fair value of RMP, EQM Olympus, Strike Force (a) and EQM WV $ 4,014,984 Estimated Fair Value of Assets Acquired and Liabilities Assumed: Current assets (b) 132,459 Intangible assets (c) 623,200 Property and equipment, net (d) 2,265,900 Other non-current assets 118 Current liabilities (b) (117,124 ) RMP $850 Million Facility (e) (266,000 ) Other non-current liabilities (e) (9,323 ) Total estimated fair value of assets acquired and liabilities assumed 2,629,230 Goodwill as of November 13, 2017 (f) 1,385,754 Impairment of goodwill (g) 261,941 Goodwill as of December 31, 2018 $ 1,123,813 (a) Includes the estimated fair value attributable to noncontrolling interest of $166 million . (b) The fair value of current assets and current liabilities were assumed to approximate their carrying values. (c) The identifiable intangible assets for customer relationships were estimated by applying a discounted cash flow approach which was adjusted for customer attrition assumptions and projected market conditions. (d) The estimated fair value of long-lived property and equipment were determined utilizing estimated replacement cost adjusted for a usage or obsolescence factor. (e) The estimated fair value of long-term liabilities was determined utilizing observable market inputs where available or estimated based on their then current carrying values. (f) 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. (g) During its annual goodwill assessment for the year ended December 31, 2018, EQM determined that carrying value of the RMP PA Gas Gathering reporting unit, which comprises the Pennsylvania gathering assets acquired in the Rice Merger, was greater than its fair value. As a result, EQM recognized an impairment to goodwill of approximately $261.9 million . The Gulfport Transaction On May 1, 2018, pursuant to the Purchase and Sale Agreement, dated April 25, 2018, by and among EQM, EQM Gathering, Gulfport Energy Corporation (Gulfport) and an affiliate of Gulfport, EQM Gathering acquired the remaining 25% limited liability company interest in Strike Force Midstream not owned by Strike Force for $175 million (the Gulfport Transaction). As a result, EQM owned 100% of Strike Force Midstream effective as of May 1, 2018. RMP and the entities part of the Drop-Down Transaction were businesses and the related acquisitions were transactions between entities under common control; therefore, EQM recorded the assets and liabilities of these entities at their carrying amounts to EQT on the date of the respective transactions. The difference between EQT's net carrying amount and the total consideration paid to EQT was recorded as a capital transaction with EQT, which resulted in a reduction in equity. This portion of the consideration was recorded in financing activities in the statements of consolidated cash flows. EQM recast its consolidated financial statements to retrospectively reflect the EQM-RMP Merger and the Drop-Down Transaction for the periods the acquired businesses were under the common control of EQT; however, the consolidated financial statements are not necessarily indicative of the results of operations that would have occurred if EQM had owned the acquired businesses during the periods reported.

Impairment of Long-Lived Assets

Impairment of Long-Lived Assets	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets EQM evaluates long-lived assets, including related intangibles, for impairment when events or changes in circumstances indicate, in management's judgment, that the carrying value of such assets may not be recoverable. Asset recoverability is measured by comparing the carrying value of the asset or asset group with its expected future pre-tax undiscounted cash flows. These cash flow estimates require EQM to make projections and assumptions for many years into the future for pricing, demand, competition, operating cost and other factors. If the carrying amount exceeds the expected future undiscounted cash flows, EQM recognizes an impairment equal to the excess of net book value over fair value as determined by quoted market prices in active markets or present value techniques if quotes are unavailable. The determination of the fair value using present value techniques requires EQM to make projections and assumptions regarding the probability of a range of outcomes and the rates of interest used in the present value calculations. Any changes EQM makes to these projections and assumptions could result in significant revisions to its evaluation of recoverability of its property, plant and equipment and the recognition of additional impairments. During the second quarter of 2019, EQM reassessed its asset groupings for its regulated pipelines due to certain regulatory ratemaking policy changes affecting the regulated pipelines, changes in strategic focus and plans for segmentation of operations. Prior to the second quarter of 2019, EQM defined its regulated asset grouping to include the FERC-regulated transmission and storage assets, integrated with the low-pressure gathering assets due to overlapping operations, shared costs structure and similar ratemaking structures. During the second quarter, EQM reached a settlement related to its FERC Form 501-G report, which was focused solely on EQM’s FERC-regulated transmission and storage assets. The settlement further differentiated the rate structures, which are primarily negotiated rates for the FERC-regulated transmission assets versus the tariff-based rate structure for the FERC-regulated low-pressure gathering assets. Further, management increased its operational focus and emphasis on high-pressure gathering assets as illustrated by the consummation of the Bolt-on Acquisition. As a result of these regulatory changes and shift in operational focus, beginning with the second quarter of 2019, EQM groups its FERC-regulated assets in two asset groupings: FERC-regulated transmission and storage assets and FERC-regulated low-pressure gathering assets. Upon the change in asset grouping, management evaluated whether any indicators of impairment were present and in conjunction with the evaluation, EQM determined that the carrying values for the non-core FERC-regulated low-pressure gathering assets exceeded their undiscounted cash flows. Additionally, following the settlement related to the FERC Form 501-G report, management does not currently plan to seek to recover the deficient cash flows through a future rate proceeding. EQM therefore estimated the fair values of FERC-related low-pressure gathering assets and determined that their fair values were not in excess of the assets’ carrying values, which resulted in recognized impairments of property and equipment of approximately $80.1 million related to the assets within EQM's Gathering segment. As a result of the impairment, the assets carry no book value.

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases As discussed in Note 1 , EQM adopted ASU 2016-02, ASU 2018-11 and ASU 2019-01 on January 1, 2019 (the Adoption Date) using the optional transition method of adoption. EQM elected a package of practical expedients that allows an entity to not reassess (i) whether a contract is or contains a lease, (ii) lease classification and (iii) initial direct costs. In addition, EQM elected the following practical expedients: (i) to not reassess certain land easements, (ii) to not apply the recognition requirements under the standard to short-term leases and (iii) to combine and account for lease and nonlease contract components as a lease, which requires the capitalization of fixed nonlease payments on the Adoption Date or lease effective date and the recognition of variable nonlease payments as variable lease expense. Nonlease payments include payments for property taxes and other operating and maintenance expenses incurred by the lessor but payable by EQM in connection with the leasing arrangement. On the Adoption Date, EQM recorded on its consolidated balance sheet an operating lease right-of-use asset and a corresponding operating lease liability of $2.3 million , reflecting the present value of future lease payments on EQM's facility and compressor lease contracts. The discount rate used to determine present value, referred to as the incremental borrowing rate, was based on the rate of interest that EQM estimated it would have to pay to borrow (on a collateralized-basis over a similar term) an amount equal to the lease payments in a similar economic environment as of the Adoption Date. EQM is required to reassess the incremental borrowing rate for any new and modified lease contracts as of the contract effective date. Adoption of the standard did not require an adjustment to the opening balance of retained earnings. As of the Adoption Date and June 30, 2019 , EQM had no lease contracts classified as financing leases and was neither a lessor nor party to a subleasing arrangement. In connection with the Shared Assets Transaction discussed in Note 2 , on March 31, 2019, Equitrans Midstream assigned to EQM two lease agreements that support EQM operations (the Shared Leases Assignment), one of which provides rights to a facility and the other to a compressor station. As a result of the Shared Leases Assignment, EQM recorded $33.0 million of right-of-use assets and corresponding operating lease liabilities. In addition, in connection with the Bolt-on Acquisition discussed in Note 2 , EQM acquired 10 compressor leases and one facilities lease for which it recorded approximately $1.3 million in operating lease expenses during the three and six months ended June 30, 2019 . EQM recorded operating lease right-of-use assets and a corresponding operating lease liability of approximately $20.0 million for these acquired leases. The following table summarizes operating lease cost for the three and six months ended June 30, 2019 . Three Months Ended June 30, 2019 Six Months Ended (Thousands) Operating lease cost $ 2,852 $ 4,149 Short-term lease cost 1,512 1,880 Variable lease cost 4 12 Total lease cost $ 4,368 $ 6,041 Operating lease expense related to EQM's compressor lease contracts and facility lease contracts is reported in operating and maintenance expense and selling, general and administrative expense, respectively, on EQM's statements of consolidated operations. For the three and six months ended June 30, 2019 , cash paid for operating lease liabilities was $2.5 million and $3.8 million , respectively, which was reported in cash flows provided by operating activities on EQM's statements of consolidated cash flows. The operating lease right-of-use assets are reported in other assets and the current and noncurrent portions of the operating lease liabilities are reported in accrued liabilities and regulatory and other long-term liabilities, respectively. As of June 30, 2019 , the operating lease right-of-use assets were $52.8 million and operating lease liabilities were $53.1 million , of which $8.8 million was classified as current. As of June 30, 2019 , the weighted average remaining lease term was 8 years and the weighted average discount rate was 6.0% . Schedule of Operating Lease Liability Maturities. The following table summarizes undiscounted cash flows owed by EQM to lessors pursuant to contractual agreements in effect as of June 30, 2019 and related imputed interest. The majority of EQM's lease agreements have multiple renewal periods at EQM's option; however, because none of the renewal periods are reasonably assured to be exercised, the associated operating lease payments have not been included in the table below. June 30, 2019 (Thousands) 2019 $ 5,619 2020 10,937 2021 9,161 2022 7,694 2023 5,607 2024 3,966 Thereafter 24,728 Total 67,712 Less: imputed interest 14,597 Present value of operating lease liability $ 53,115

Equity

Equity	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Equity	Equity The following table summarizes changes in EQM's Series A Preferred Units, common units and Class B units, each representing limited partner interests in EQM, and general partner units during the year ended December 31, 2018 and from January 1, 2019 through June 30, 2019 . Limited Partner Interests Series A Preferred Units Common Units Class B Units General Partner Units Total Balance at January 1, 2018 — 80,581,758 — 1,443,015 82,024,773 Common units issued (1) — 10,821 — — 10,821 Drop-Down Transaction consideration — 5,889,282 — — 5,889,282 Common units issued in the EQM-RMP Merger — 33,975,777 — — 33,975,777 Balance at December 31, 2018 — 120,457,638 — 1,443,015 121,900,653 Unit cancellation — (8 ) — — (8 ) EQM IDR Transaction (2) — 80,000,000 7,000,000 (1,443,015 ) 85,556,985 Issuance of Series A Preferred Units 24,605,291 — — — 24,605,291 Balance at June 30, 2019 24,605,291 200,457,630 7,000,000 — 232,062,921 (1) Units issued upon the resignation of a member of the Board of Directors of EQM's general partner. (2) In exchange for the cancellation of the EQM IDRs, EQM issued 87,000,000 EQM common units (the Exchange Consideration) to the Former EQM General Partner. At the effective time of the EQM IDR Merger, (i) the Exchange Consideration held by the Former EQM General Partner was canceled, (ii) 80,000,000 EQM common units and 7,000,000 Class B units were issued on a pro rata basis to certain affiliates of Equitrans Midstream, and (iii) 21,811,643 EQM common units held by EQGP were canceled and 21,811,643 EQM common units were issued pro rata to certain affiliates of Equitrans Midstream. As of June 30, 2019 , Equitrans Gathering Holdings, LLC (Equitrans Gathering Holdings), EQM GP Corporation (EQM GP Corp) and Equitrans Midstream Holdings, LLC (EMH), each a wholly-owned subsidiary of Equitrans Midstream, held 89,505,616 , 89,536 and 27,650,303 EQM common units, respectively. Additionally, Equitrans Gathering Holdings, EQM GP Corp and EMH held 6,153,907 , 6,155 and 839,938 Class B units, respectively. As of June 30, 2019 , Equitrans Midstream owned, directly or indirectly, 117,245,455 EQM common units and 7,000,000 Class B units (collectively representing, after taking into account the Series A Preferred Units issued in the Private Placement on an as-converted basis, a 53.5% limited partner interest in EQM) and the entire non-economic general partner interest in EQM, while the public owned a 46.5% limited partner interest in EQM. Following the completion of the Private Placement, certain investors owned an aggregate of 24,605,291 Series A Preferred Units. Class B Units As discussed above and in Note 1 , in February 2019, EQM issued 7,000,000 Class B units representing a new class of limited partner interests in EQM as partial consideration for the EQM IDR Transaction. The Class B units are substantially similar in all respects to EQM's common units, except that the Class B units are not entitled to receive distributions of available cash until the applicable Class B unit conversion date (or, if earlier, a change of control). The Class B units are divided into three tranches, with the first tranche of 2,500,000 Class B units becoming convertible at the holder’s option into EQM common units on April 1, 2021, the second tranche of 2,500,000 Class B units becoming convertible at the holder’s option into EQM common units on April 1, 2022, and the third tranche of 2,000,000 Class B units becoming convertible at the holder’s option on April 1, 2023 (each, a Class B unit conversion date). Additionally, the Class B units will become convertible at the holder’s option into EQM common units immediately before a change of control of EQM. After the applicable Class B unit conversion date (or, if earlier, a change of control), 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. The holders of Class B units vote together with the holders of EQM common units as a single class, except that Class B units owned by the general partner of EQM and its affiliates are excluded from voting if EQM common units owned by such parties are excluded from voting. Holders of Class B units are 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 EQM partnership interests in any material respect or as required by law. Series A Preferred Units As discussed in Note 1 , in March 2019, EQM entered into the Preferred Unit Purchase Agreement with certain investors to issue and sell in a private placement an aggregate of 24,605,291 Series A Preferred Units representing limited partner interests in EQM for a cash purchase price of $48.77 per Series A Preferred Unit, resulting in total gross proceeds of approximately $1.2 billion . The net proceeds from the Private Placement were used in part to fund the purchase price in the Bolt-on Acquisition and to pay certain fees and expenses related to the Bolt-on Acquisition, and the remainder was used for general partnership purposes. The Private Placement closed concurrently with the closing of the Bolt-on Acquisition on April 10, 2019 . The Series A Preferred Units rank senior to all common units and Class B units representing limited partner interests in EQM with respect to distribution rights and rights upon liquidation. The Series A Preferred Units will vote on an as-converted basis with the EQM common units and Class B units and will have certain other class voting rights with respect to any amendment to EQM's partnership agreement or its certificate of limited partnership that would be adverse (other than in a de minimis manner) to any of the rights, preferences or privileges of the Series A Preferred Units. The holders of the Series A Preferred Units are entitled to receive cumulative quarterly distributions at a rate of $1.0364 per Series A Preferred Unit for the first twenty distribution periods, and thereafter the quarterly distributions on the Series A Preferred Units will be an amount per Series A Preferred Unit for such quarter equal to (i) the Series A Preferred Unit purchase price of $48.77 per such unit, multiplied by (ii) a percentage equal to the sum of (A) the greater of (x) the 3-month LIBOR as of the second London banking day prior to the beginning of the applicable quarter and (y) 2.59% , and (B) 6.90% , multiplied by (iii) 25% . EQM will not be entitled to pay any distributions on any junior securities, including any EQM common units, prior to paying the quarterly distributions payable to the holders of Series A Preferred Units, including any previously accrued and unpaid distributions. Each holder of the Series A Preferred Units may elect to convert all or any portion of the Series A Preferred Units owned by it into EQM common units initially on a one-for-one basis, subject to customary anti-dilution adjustments and an adjustment for any distributions that have accrued but have not been paid when due and partial period distributions, at any time (but not more often than once per fiscal quarter) after April 10, 2021 (or earlier liquidation, dissolution or winding up of EQM), provided that any conversion is for at least $30 million (calculated based on the closing price of the EQM common units on the trading day preceding notice of conversion) or such lesser amount if such conversion relates to all of a holder’s remaining Series A Preferred Units. EQM may elect to convert all or any portion of the Series A Preferred Units into EQM common units at any time (but not more often than once per quarter) after April 10, 2021 if (i) the common units are listed for, or admitted to, trading on a national securities exchange, (ii) the closing price per common unit on the national securities exchange on which the common units are listed for, or admitted to, trading exceeds 140% of the Series A Preferred Unit purchase price of $48.77 per such unit for the 20 consecutive trading days immediately preceding notice of the conversion, (iii) the average daily trading volume of the common units on the national securities exchange on which the common units are listed for, or admitted to, trading exceeds 500,000 common units for the 20 consecutive trading days immediately preceding notice of the conversion, (iv) EQM has an effective registration statement on file with the SEC covering resales of the common units to be received by such holders upon any such conversion and (v) EQM has paid all accrued quarterly distributions in cash to the holders. In addition, upon certain events involving a change in control, the holders of Series A Preferred Units may elect, among other potential elections, to convert their preferred units into EQM common units at a certain conversion rate. Net Income per Limited Partner Unit and Cash Distributions Net Income per Limited Partner Unit. Net income per limited partner unit is calculated utilizing the two-class method by dividing the limited partner interest in net income by the weighted average number of limited partner units outstanding during the period. The two-class method uses an earnings allocation method under which earnings per limited partner unit are calculated for each class of common unit and any participating security considering all distributions declared and participation rights in undistributed earnings as if all earnings had been distributed during the period. Diluted net income per limited partner unit reflects the potential dilution that could occur if securities or agreements to issue common units were exercised, settled or converted into EQM common units. EQM uses the if-converted method to compute potential common units from phantom units granted to independent and non-employee directors and the if-converted method to compute potential common units related to the conversion of Series A Preferred Units and Class B units. Under the if-converted method, dilutive convertible securities are assumed to be converted from the date of the issuance, and the resulting common units are included in the denominator of the diluted net income per unit calculation for the period being presented. Each series of potential common units is evaluated in sequence from the most dilutive to the least dilutive. Distributions declared in the period and undeclared distributions on the cumulative Series A Preferred Units that accumulated during the period are added back to the numerator for purposes of the if-converted calculation. As a result of the EQM IDR Transaction, EQM’s common unitholders are entitled to all distributions until the Class B units are converted to common units (other than distributions in respect of the Series A Preferred Units following the initial distribution period for such Series A Preferred Units commencing with the quarter ended June 30, 2019 ). Class B unitholders have no rights to distributions until they are convertible into common units. Accordingly, for all periods prior to the date such Class B units are convertible, the Class B units are not considered participating securities under the two-class method. In addition, the Series A Preferred Units are not considered a participating security as they only have distribution rights up to the specified per-unit quarterly distribution and have no rights to EQM’s undistributed earnings prior to conversion of the Series A Preferred Units into EQM common units, as discussed in Note 5 . For the three and six months ended June 30, 2019 , limited partner interest in net income, which excludes the Series A Preferred Units interest in net income, was fully allocated to EQM’s common unitholders. For the three and six months ended June 30, 2018 , net income attributable to EQM was allocated to the general partner and limited partners in accordance with their respective ownership percentages. Any common units issued during the relevant periods are included on a monthly weighted-average basis for the periods in which they were outstanding. The phantom units granted to the independent and non-employee directors of EQM's general partner will be paid in common units on a director’s termination of service on the Board of Directors of EQM's general partner. The weighted average phantom unit awards included in the calculation of basic weighted average limited partner units outstanding were 24,007 and 21,041 for the three months ended June 30, 2019 and 2018 , respectively, and 22,896 and 20,506 for the six months ended June 30, 2019 and 2018, respectively. The following table presents EQM's calculation of net income per limited partner unit for common and Class B limited partner units. Three Months Ended Six Months Ended 2019 2018 (1) 2019 2018 (1) (Thousands, except per unit data) Net income attributable to EQM $ 152,438 $ 233,832 $ 404,369 $ 494,182 Less: Series A Preferred Units interest in net income (22,979 ) — (22,979 ) — Less: pre-acquisition net income allocated to parent — (72,620 ) — (155,752 ) Less: general partner interest in net income – general partner units — (1,700 ) — (4,791 ) Less: general partner interest in net income – IDRs — (68,121 ) — (112,285 ) Limited partner interest in net income $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to common units $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to Class B units $ — $ — $ — $ — Weighted average limited partner common units outstanding - basic 200,482 83,553 177,498 82,290 Weighted average limited partner common units outstanding - diluted (2) 207,482 83,553 195,645 82,290 Net income per limited partner common unit - basic $ 0.65 $ 1.09 $ 2.15 $ 2.69 Net income per limited partner common unit - diluted $ 0.62 $ 1.09 $ 2.07 $ 2.69 (1) Net income attributable to the Drop-Down Transaction and the EQM-RMP Merger for the periods prior to May 1, 2018 and July 23, 2018, respectively, was not allocated to the limited partners for purposes of calculating net income per limited partner unit as these pre-acquisition amounts were not available to the EQM unitholders. (2) For the three months ended June 30, 2019, 7,000,000 Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. The effect of Series A Preferred Units was anti-dilutive. For the six months ended June 30, 2019, 7,000,000 Class B units and 11,147,148 Series A Preferred Units and Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. Class B units are not a participating security as they do not participate in distributions. Distributions to common unitholders. On July 24, 2019 , the Board of Directors of EQM's general partner declared a cash distribution to EQM's unitholders for the second quarter of 2019 of $1.160 per common unit. The cash distribution will be paid on August 13, 2019 to common unitholders of record at the close of business on August 2, 2019 . Based on the EQM common units outstanding on July 30, 2019 , cash distributions paid by EQM to Equitrans Midstream will be approximately $136.0 million related to Equitrans Midstream's limited partner interest in EQM. Distributions to Series A Preferred Unit holders. On July 24, 2019 , the Board of Directors of EQM's general partner declared a quarterly cash distribution on the Series A Preferred Units for the second quarter of 2019 of $0.9339 per Series A Preferred Unit, which amount reflected pro-ration in accordance with the Fourth Amended and Restated Agreement of Limited Partnership of EQM, dated April 10, 2019. The cash distribution will be paid on August 13, 2019 to Series A Preferred unitholders of record at the close of business on August 2, 2019 . For the quarter ended June 30, 2019 , no distributions were declared on the Class B units as none of these units were convertible into EQM common units.

Financial Information by Busine

Financial Information by Business Segment	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Financial Information by Business Segment	Financial Information by Business Segment EQM reports its operations in three segments that reflect its three lines of business: Gathering, Transmission and Water. Gathering includes EQM's high-pressure gathering lines and FERC-regulated low-pressure gathering line; Transmission includes EQM's FERC-regulated interstate pipelines and storage system; and Water consists of EQM's water pipelines, impoundment facilities, pumping stations, take point facilities and measurement facilities. Three Months Ended Six Months Ended 2019 2018 2019 2018 (Thousands) Revenues from customers (including related parties): Gathering $ 285,666 $ 241,189 $ 547,547 $ 478,579 Transmission 92,767 89,145 202,626 196,079 Water 27,734 44,363 45,776 71,065 Total operating revenues $ 406,167 $ 374,697 $ 795,949 $ 745,723 Operating income: Gathering $ 94,131 $ 161,818 $ 276,209 $ 332,853 Transmission 63,244 60,642 147,994 140,093 Water 10,072 23,408 11,258 38,720 Total operating income $ 167,447 $ 245,868 $ 435,461 $ 511,666 Reconciliation of operating income to net income: Equity income (a) $ 36,782 $ 10,938 $ 67,845 $ 19,749 Other income 1,959 944 4,169 1,848 Net interest expense 49,717 23,065 99,073 35,735 Net income $ 156,471 $ 234,685 $ 408,402 $ 497,528 (a) Equity income is included in the Transmission segment. June 30, December 31, (Thousands) Segment assets: Gathering $ 8,031,401 $ 6,011,654 Transmission (a) 3,636,355 3,066,659 Water 262,773 237,602 Total operating segments 11,930,529 9,315,915 Headquarters, including cash 132,641 140,206 Total assets $ 12,063,170 $ 9,456,121 (a) The equity investment in the MVP Joint Venture is included in the Transmission segment. Three Months Ended Six Months Ended 2019 2018 2019 2018 (Thousands) Depreciation: Gathering $ 37,443 $ 23,882 $ 65,559 $ 46,950 Transmission 12,594 12,430 25,127 24,871 Water 6,478 5,798 12,894 11,569 Total $ 56,515 $ 42,110 $ 103,580 $ 83,390 Expenditures for segment assets: Gathering (1)(2) $ 265,198 $ 186,457 $ 472,915 $ 320,595 Transmission (3) 11,229 27,962 29,991 46,891 Water 8,849 7,002 18,024 9,377 Total (4) $ 285,276 $ 221,421 $ 520,930 $ 376,863 (1) Includes approximately $8.9 million and $58.6 million for the three and six months ended June 30, 2019 , respectively, related to non-operating assets acquired from Equitrans Midstream in the Shared Assets Transaction that primarily support EQM's gathering activities. (2) Includes approximately $10.9 million of capital expenditures related to noncontrolling interests in Eureka Midstream for the three and six months ended June 30, 2019 . (3) Transmission capital expenditures do not include capital contributions made to the MVP Joint Venture for the MVP and MVP Southgate projects of approximately $156.4 million and $65.8 million for the three months ended June 30, 2019 and 2018 , respectively, and approximately $301.2 million and $182.8 million for the six months ended June 30, 2019 and 2018 , respectively. (4) EQM accrues capital expenditures when work has been completed but the associated bills have not yet been paid. These accrued amounts are excluded from capital expenditures in the statements of consolidated cash flows until they are paid. Accrued capital expenditures were approximately $110.8 million , $137.8 million and $108.9 million at June 30, 2019 , March 31, 2019 and December 31, 2018 , respectively. Accrued capital expenditures were approximately $84.6 million , $75.5 million and $90.7 million at June 30, 2018 , March 31, 2018 and December 31, 2017 , respectively. On April 10, 2019, as a result of the Bolt-on Acquisition, EQM assumed $8.8 million of Eureka Midstream accrued capital expenditures.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers For the three and six months ended June 30, 2019 and 2018 , all revenues recognized on EQM's statements of consolidated operations are from contracts with customers. As of June 30, 2019 and December 31, 2018 , all receivables recorded on EQM's consolidated balance sheets represent performance obligations that have been satisfied and for which an unconditional right to consideration exists. Summary of disaggregated revenues . The tables below provide disaggregated revenue information by business segment. Three Months Ended June 30, 2019 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 147,771 $ 81,836 $ — $ 229,607 Volumetric-based fee revenues 137,895 10,931 — 148,826 Water services revenues — — 27,734 27,734 Total operating revenues $ 285,666 $ 92,767 $ 27,734 $ 406,167 Three Months Ended June 30, 2018 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 111,702 $ 82,222 $ — $ 193,924 Volumetric-based fee revenues 129,487 6,923 — 136,410 Water services revenues — — 44,363 44,363 Total operating revenues $ 241,189 $ 89,145 $ 44,363 $ 374,697 Six Months Ended June 30, 2019 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 276,730 $ 181,060 $ — $ 457,790 Volumetric-based fee revenues 270,817 21,566 — 292,383 Water service revenues — — 45,776 45,776 Total operating revenues $ 547,547 $ 202,626 $ 45,776 $ 795,949 Six Months Ended June 30, 2018 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 221,635 $ 179,997 $ — $ 401,632 Volumetric-based fee revenues 256,944 16,082 — 273,026 Water service revenues — — 71,065 71,065 Total operating revenues $ 478,579 $ 196,079 $ 71,065 $ 745,723 Summary of Remaining Performance Obligations. The following table summarizes the transaction price allocated to EQM's remaining performance obligations under all contracts with firm reservation fees and minimum volume commitments (MVCs) as of June 30, 2019 . 2019 (a) 2020 2021 2022 2023 Thereafter Total (Thousands) Gathering firm reservation fees $ 253,531 $ 566,813 $ 614,356 $ 614,356 $ 614,264 $ 2,647,183 $ 5,310,503 Gathering revenues supported by MVCs 45,877 95,294 100,715 100,715 100,715 309,214 752,530 Transmission firm reservation fees 163,370 334,627 345,527 340,453 336,333 2,478,310 3,998,620 Total $ 462,778 $ 996,734 $ 1,060,598 $ 1,055,524 $ 1,051,312 $ 5,434,707 $ 10,061,653 (a) July 1, 2019 through December 31, 2019. 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 EQM has executed firm contracts, EQM'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 June 30, 2019 .

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Pursuant to an omnibus agreement (the ETRN Omnibus Agreement), Equitrans Midstream performs centralized corporate, general and administrative services for EQM. In exchange, EQM reimburses Equitrans Midstream for the expenses incurred by Equitrans Midstream in providing these services. In connection with the entry into the Assignment and Bill of Sale, the ETRN Omnibus Agreement was amended and restated, to, among other things, govern Equitrans Midstream's use, and payment for such use, of the acquired assets following their conveyance to EQM. Pursuant to a secondment agreement, employees of Equitrans Midstream and its affiliates may be seconded to EQM to provide operating and other services with respect to EQM's business under the direction, supervision and control of EQM. EQM reimburses Equitrans Midstream and its affiliates for the services provided by the seconded employees. The expenses for which EQM reimburses Equitrans Midstream and its affiliates may not necessarily reflect the actual expenses that EQM would incur on a stand-alone basis. EQM is unable to estimate what those expenses would be on a stand-alone basis. In connection with the Separation, Equitrans Midstream assumed certain obligations from EQT to indemnify and reimburse EQM. As of June 30, 2019 , EQT remained a related party following the Separation due to its 19.9% ownership interest in Equitrans Midstream. In the ordinary course of business, EQM engaged, and continues to engage, in transactions with EQT and its affiliates, including, but not limited to and as applicable, gathering agreements, transportation service and precedent agreements, storage agreements and water service agreements.

Investment in Unconsolidated En

Investment in Unconsolidated Entity	6 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Entity	Investment in Unconsolidated Entity The MVP Joint Venture is constructing the Mountain Valley Pipeline (MVP), an estimated 300 -mile natural gas interstate pipeline that will span from northern West Virginia to southern Virginia. EQM is the operator of the MVP and owned a 45.5% interest in the MVP project as of June 30, 2019 . 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. EQM is not the primary beneficiary of the MVP Joint Venture because it does not have the power to direct the activities that most significantly affect the MVP Joint Venture's economic performance. Certain business decisions, such as decisions to make distributions of cash, 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. As of June 30, 2019 , EQM had a 47.2% ownership interest in the MVP Southgate project and will operate the pipeline. In May 2019 , the MVP Joint Venture issued a capital call notice for the funding of the MVP project to MVP Holdco, LLC (MVP Holdco), a direct, wholly-owned subsidiary of EQM, for $352.3 million , of which $93.4 million was paid in July 2019 and $114.3 million and $144.5 million is expected to be paid in August 2019 and September 2019 , respectively. In addition, in May 2019, the MVP Joint Venture issued a capital call notice for the funding of the MVP Southgate project to MVP Holdco for $4.0 million , of which $0.9 million was paid in July 2019 and $1.6 million and $1.5 million is expected to be paid in August 2019 and September 2019 , respectively. The capital contribution payable and the corresponding increase to the investment balance are reflected on the consolidated balance sheet as of June 30, 2019 . The interests in MVP and MVP Southgate are equity method investments for accounting purposes because EQM has the ability to exercise significant influence, but not control, 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 EQM's statements of consolidated operations. 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. In January 2019, EQM issued a performance guarantee in an amount equal to 33% of EQM's proportionate share of the then-remaining construction budget for the MVP project, which was $261 million at the time of issuance. As of June 30, 2019 , EQM was obligated to issue a performance guarantee in an amount equal to approximately $280 million based on the updated construction budget for the MVP project and capital contributions made during the first and second quarters of 2019. Effective July 1, 2019, EQM restated the performance guarantee to an amount equal to approximately $249 million , which reflected a decrease as result of a capital contribution made on July 1, 2019. 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. As of June 30, 2019 , EQM's maximum financial statement exposure related to the MVP Joint Venture was approximately $2,004 million , which consists of the investment in unconsolidated entity balance on the consolidated balance sheet as of June 30, 2019 , net of capital contributions payable, and amounts that could have become due under EQM's performance guarantees as of that date. The following tables summarize the unaudited condensed consolidated financial statements of the MVP Joint Venture. Condensed Consolidated Balance Sheets June 30, December 31, (Thousands) Current assets $ 836,397 $ 687,657 Non-current assets 4,033,475 3,223,220 Total assets $ 4,869,872 $ 3,910,877 Current liabilities $ 420,534 $ 617,355 Non-current liabilities 2,166 — Equity 4,447,172 3,293,522 Total liabilities and equity $ 4,869,872 $ 3,910,877 Condensed Statements of Consolidated Operations Three Months Ended Six Months Ended 2019 2018 2019 2018 (Thousands) Environmental remediation reserve $ 26 $ — $ (2,166 ) $ — Other income 1,785 743 4,698 1,277 Net interest income 23,700 6,989 43,935 12,638 AFUDC - equity 55,298 16,307 102,514 29,489 Net income $ 80,809 $ 24,039 $ 148,981 $ 43,404

Debt

Debt	6 Months Ended
	Jun. 30, 2019
Long-term Debt, Current and Noncurrent [Abstract]
Debt	Debt $3 Billion Facility. On October 31, 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 $3 Billion Facility). The $3 Billion 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 $3 Billion Facility has an accordion feature that allows EQM to increase the available borrowings under the facility by up to an additional $750 million . The $3 Billion 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 $3 Billion 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 $3 Billion Facility are unsecured. EQM's $3 Billion Facility contains negative covenants that, among other things, limit restricted payments, the incurrence of debt, dispositions, mergers and fundamental changes, and transactions with affiliates. In addition, the $3 Billion 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 $3 Billion 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 June 30, 2019 , EQM had approximately $1.1 billion of borrowings outstanding and $1 million of letters of credit outstanding under the $3 Billion Facility. As of December 31, 2018 , EQM had approximately $625 million of borrowings outstanding and $1 million of letters of credit outstanding under the $3 Billion Facility. During the three and six months ended June 30, 2019 , the maximum amount of EQM's outstanding borrowings under the $3 Billion Facility at any time was approximately $1.2 billion and the average daily balance was approximately $1,043 million and $993 million , respectively. EQM incurred interest at weighted average annual interest rates of approximately 3.8% and 3.9% for the three and six months ended June 30, 2019 , respectively. During the three and six months ended June 30, 2018 , the maximum amount of EQM's outstanding borrowings under the $3 Billion Facility at any time was approximately $338 million and $420 million , respectively, and the average daily balance was approximately $122 million and $211 million , respectively. EQM incurred interest at weighted average annual interest rates of approximately 3.4% and 3.2% for the three and six months ended June 30, 2018 , respectively. Eureka Credit Facility. Eureka Midstream, LLC (Eureka), a wholly owned subsidiary of Eureka Midstream, has a $400 million revolving credit facility, which is available for general business purposes, including financing maintenance and expansion capital expenditures related to the Eureka system and providing working capital for Eureka’s operations (the Eureka Credit Facility). Subject to satisfaction of certain conditions, the Eureka Credit Facility has an accordion feature that allows Eureka to increase the available borrowings under the facility by an additional $100 million to an aggregate $500 million of total commitments. Under the terms of the Eureka Credit Facility, Eureka can obtain base rate loans or Eurodollar rate loans. Base rate loans are denominated in dollars and bear interest at an adjusted base rate, which was equal to the higher of (i) JPMorgan Chase Bank, N.A.'s prime rate, (ii) the one-month Adjusted Eurodollar Rate (as defined in the Eureka Credit Facility credit agreement) plus 1.0% or (iii) the Federal Funds effective rate plus 0.5% per annum; plus the Applicable Margin, as described below. Eurodollar rate loans bear interest at the Adjusted Eurodollar Rate per annum, which rate is to be determined by the administrative agent pursuant to a prescribed calculation based on the ICE Benchmark Administration LIBOR Rate plus the Applicable Margin. The Applicable Margin ranged from 0.75% to 2.0% in the case of base rate loans and from 1.75% to 3.0% in the case of Eurodollar loans, in each case, depending on the amount of the loan outstanding in relation to the borrowing base. The Eureka Credit Facility contains negative covenants that, among other things, limit restricted payments, the incurrence of debt, dispositions, mergers and fundamental changes, securities issuances, and transactions with affiliates. In addition, the Eureka Credit Facility contains events of default such as insolvency, nonpayment of scheduled principal or interest obligations, loss of material contracts, change of control and cross-default related to the acceleration or default of certain other financial obligations. Under the Eureka Credit Facility, Eureka is required to maintain a consolidated leverage ratio of not more than 4.75 to 1.00 (or not more than 5.25 to 1.00 for certain measurement periods following the consummation of certain acquisitions). Additionally, as of the end of any fiscal quarter, Eureka will not permit the ratio of consolidated EBITDA (as defined in the Eureka Credit Facility) for the four fiscal quarters then ending to consolidated interest charges to be less than 2.50 to 1.00 . As of June 30, 2019 , Eureka had approximately $293 million of borrowings outstanding under the Eureka Credit Facility. For the period from April 10, 2019 through June 30, 2019 , the maximum amount of outstanding borrowings under the Eureka Credit Facility at any time was approximately $293 million , the average daily balance was approximately $277 million and Eureka incurred interest at a weighted average annual interest rate of approximately 4.5% . EQM Term Loan Facility . On April 25, 2018, EQM entered into a $2.5 billion unsecured multi-draw 364 -day term loan facility with a syndicate of lenders (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 2018 Senior Notes (defined below), on June 25, 2018, the balance outstanding 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. From April 25, 2018 through June 25, 2018, the maximum amount of EQM's outstanding borrowings under the EQM Term Loan Facility at any time was approximately $1,825 million and the average daily balance was approximately $1,231 million . EQM incurred interest at a weighted average annual interest rate of approximately 3.3% for the period from April 25, 2018 through June 25, 2018. RMP $850 Million Facility. RM Operating LLC (formerly Rice Midstream OpCo LLC), a wholly-owned subsidiary of RMP, had an $850 million credit facility (the RMP $850 million Facility). In connection with the completion of the EQM-RMP Merger, on July 23, 2018, EQM repaid the approximately $260 million of borrowings outstanding under the RMP $850 Million Facility and the RMP $850 Million Facility was terminated. Prior to its termination, the RMP $850 Million 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. The RMP $850 Million Facility was secured by mortgages and other security interests on substantially all of RMP's properties and was guaranteed by RMP and its restricted subsidiaries. During the three and six months ended June 30, 2018 , the maximum outstanding borrowings were approximately $325 million and $336 million , respectively, the average daily balance was approximately $305 million and $306 million , respectively, and the weighted average annual interest rate for the period was approximately 3.9% and 3.8% , respectively. 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 a predecessor to the $3 Billion 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 a predecessor to the $3 Billion 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. 2018 Senior Notes. During the second quarter of 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 2018 Senior Notes). EQM received net proceeds from the offering of approximately $2,465.8 million , inclusive of a discount of $11.8 million and estimated debt issuance costs of approximately $22.4 million . The net proceeds were used to repay the balances outstanding under the EQM Term Loan Facility and the RMP $850 Million Facility, and the remainder was used for general partnership purposes. The 2018 Senior Notes were issued pursuant to new supplemental indentures to EQM's existing indenture dated August 1, 2014. The 2018 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. As of June 30, 2019 , EQM and Eureka were in compliance with all debt provisions and covenants.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The carrying values of cash and cash equivalents, accounts receivable, amounts due to/from related parties and accounts payable approximate fair value due to the short maturity of the instruments; as such, their fair values are Level 1 fair value measurements. The carrying value of the credit facility borrowings approximates fair value as the interest rates are based on prevailing market rates; this is considered a Level 1 fair value measurement. As 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. As of June 30, 2019 and December 31, 2018 , the estimated fair value of EQM's senior notes was approximately $3,612 million and $3,425 million , respectively, and the carrying value of EQM's senior notes was approximately $3,459 million and $3,457 million , respectively. The fair value of the Preferred Interest is a Level 3 fair value measurement and is estimated using an income approach model that applies a market-based discount rate. As of June 30, 2019 and December 31, 2018 , the estimated fair value of the Preferred Interest was approximately $127 million and $122 million , respectively, and the carrying value of the Preferred Interest was approximately $112 million and $115 million , respectively.

Net Income per Limited Partner

Net Income per Limited Partner Unit and Cash Distributions	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Income per Limited Partner Unit and Cash Distributions	Equity The following table summarizes changes in EQM's Series A Preferred Units, common units and Class B units, each representing limited partner interests in EQM, and general partner units during the year ended December 31, 2018 and from January 1, 2019 through June 30, 2019 . Limited Partner Interests Series A Preferred Units Common Units Class B Units General Partner Units Total Balance at January 1, 2018 — 80,581,758 — 1,443,015 82,024,773 Common units issued (1) — 10,821 — — 10,821 Drop-Down Transaction consideration — 5,889,282 — — 5,889,282 Common units issued in the EQM-RMP Merger — 33,975,777 — — 33,975,777 Balance at December 31, 2018 — 120,457,638 — 1,443,015 121,900,653 Unit cancellation — (8 ) — — (8 ) EQM IDR Transaction (2) — 80,000,000 7,000,000 (1,443,015 ) 85,556,985 Issuance of Series A Preferred Units 24,605,291 — — — 24,605,291 Balance at June 30, 2019 24,605,291 200,457,630 7,000,000 — 232,062,921 (1) Units issued upon the resignation of a member of the Board of Directors of EQM's general partner. (2) In exchange for the cancellation of the EQM IDRs, EQM issued 87,000,000 EQM common units (the Exchange Consideration) to the Former EQM General Partner. At the effective time of the EQM IDR Merger, (i) the Exchange Consideration held by the Former EQM General Partner was canceled, (ii) 80,000,000 EQM common units and 7,000,000 Class B units were issued on a pro rata basis to certain affiliates of Equitrans Midstream, and (iii) 21,811,643 EQM common units held by EQGP were canceled and 21,811,643 EQM common units were issued pro rata to certain affiliates of Equitrans Midstream. As of June 30, 2019 , Equitrans Gathering Holdings, LLC (Equitrans Gathering Holdings), EQM GP Corporation (EQM GP Corp) and Equitrans Midstream Holdings, LLC (EMH), each a wholly-owned subsidiary of Equitrans Midstream, held 89,505,616 , 89,536 and 27,650,303 EQM common units, respectively. Additionally, Equitrans Gathering Holdings, EQM GP Corp and EMH held 6,153,907 , 6,155 and 839,938 Class B units, respectively. As of June 30, 2019 , Equitrans Midstream owned, directly or indirectly, 117,245,455 EQM common units and 7,000,000 Class B units (collectively representing, after taking into account the Series A Preferred Units issued in the Private Placement on an as-converted basis, a 53.5% limited partner interest in EQM) and the entire non-economic general partner interest in EQM, while the public owned a 46.5% limited partner interest in EQM. Following the completion of the Private Placement, certain investors owned an aggregate of 24,605,291 Series A Preferred Units. Class B Units As discussed above and in Note 1 , in February 2019, EQM issued 7,000,000 Class B units representing a new class of limited partner interests in EQM as partial consideration for the EQM IDR Transaction. The Class B units are substantially similar in all respects to EQM's common units, except that the Class B units are not entitled to receive distributions of available cash until the applicable Class B unit conversion date (or, if earlier, a change of control). The Class B units are divided into three tranches, with the first tranche of 2,500,000 Class B units becoming convertible at the holder’s option into EQM common units on April 1, 2021, the second tranche of 2,500,000 Class B units becoming convertible at the holder’s option into EQM common units on April 1, 2022, and the third tranche of 2,000,000 Class B units becoming convertible at the holder’s option on April 1, 2023 (each, a Class B unit conversion date). Additionally, the Class B units will become convertible at the holder’s option into EQM common units immediately before a change of control of EQM. After the applicable Class B unit conversion date (or, if earlier, a change of control), 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. The holders of Class B units vote together with the holders of EQM common units as a single class, except that Class B units owned by the general partner of EQM and its affiliates are excluded from voting if EQM common units owned by such parties are excluded from voting. Holders of Class B units are 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 EQM partnership interests in any material respect or as required by law. Series A Preferred Units As discussed in Note 1 , in March 2019, EQM entered into the Preferred Unit Purchase Agreement with certain investors to issue and sell in a private placement an aggregate of 24,605,291 Series A Preferred Units representing limited partner interests in EQM for a cash purchase price of $48.77 per Series A Preferred Unit, resulting in total gross proceeds of approximately $1.2 billion . The net proceeds from the Private Placement were used in part to fund the purchase price in the Bolt-on Acquisition and to pay certain fees and expenses related to the Bolt-on Acquisition, and the remainder was used for general partnership purposes. The Private Placement closed concurrently with the closing of the Bolt-on Acquisition on April 10, 2019 . The Series A Preferred Units rank senior to all common units and Class B units representing limited partner interests in EQM with respect to distribution rights and rights upon liquidation. The Series A Preferred Units will vote on an as-converted basis with the EQM common units and Class B units and will have certain other class voting rights with respect to any amendment to EQM's partnership agreement or its certificate of limited partnership that would be adverse (other than in a de minimis manner) to any of the rights, preferences or privileges of the Series A Preferred Units. The holders of the Series A Preferred Units are entitled to receive cumulative quarterly distributions at a rate of $1.0364 per Series A Preferred Unit for the first twenty distribution periods, and thereafter the quarterly distributions on the Series A Preferred Units will be an amount per Series A Preferred Unit for such quarter equal to (i) the Series A Preferred Unit purchase price of $48.77 per such unit, multiplied by (ii) a percentage equal to the sum of (A) the greater of (x) the 3-month LIBOR as of the second London banking day prior to the beginning of the applicable quarter and (y) 2.59% , and (B) 6.90% , multiplied by (iii) 25% . EQM will not be entitled to pay any distributions on any junior securities, including any EQM common units, prior to paying the quarterly distributions payable to the holders of Series A Preferred Units, including any previously accrued and unpaid distributions. Each holder of the Series A Preferred Units may elect to convert all or any portion of the Series A Preferred Units owned by it into EQM common units initially on a one-for-one basis, subject to customary anti-dilution adjustments and an adjustment for any distributions that have accrued but have not been paid when due and partial period distributions, at any time (but not more often than once per fiscal quarter) after April 10, 2021 (or earlier liquidation, dissolution or winding up of EQM), provided that any conversion is for at least $30 million (calculated based on the closing price of the EQM common units on the trading day preceding notice of conversion) or such lesser amount if such conversion relates to all of a holder’s remaining Series A Preferred Units. EQM may elect to convert all or any portion of the Series A Preferred Units into EQM common units at any time (but not more often than once per quarter) after April 10, 2021 if (i) the common units are listed for, or admitted to, trading on a national securities exchange, (ii) the closing price per common unit on the national securities exchange on which the common units are listed for, or admitted to, trading exceeds 140% of the Series A Preferred Unit purchase price of $48.77 per such unit for the 20 consecutive trading days immediately preceding notice of the conversion, (iii) the average daily trading volume of the common units on the national securities exchange on which the common units are listed for, or admitted to, trading exceeds 500,000 common units for the 20 consecutive trading days immediately preceding notice of the conversion, (iv) EQM has an effective registration statement on file with the SEC covering resales of the common units to be received by such holders upon any such conversion and (v) EQM has paid all accrued quarterly distributions in cash to the holders. In addition, upon certain events involving a change in control, the holders of Series A Preferred Units may elect, among other potential elections, to convert their preferred units into EQM common units at a certain conversion rate. Net Income per Limited Partner Unit and Cash Distributions Net Income per Limited Partner Unit. Net income per limited partner unit is calculated utilizing the two-class method by dividing the limited partner interest in net income by the weighted average number of limited partner units outstanding during the period. The two-class method uses an earnings allocation method under which earnings per limited partner unit are calculated for each class of common unit and any participating security considering all distributions declared and participation rights in undistributed earnings as if all earnings had been distributed during the period. Diluted net income per limited partner unit reflects the potential dilution that could occur if securities or agreements to issue common units were exercised, settled or converted into EQM common units. EQM uses the if-converted method to compute potential common units from phantom units granted to independent and non-employee directors and the if-converted method to compute potential common units related to the conversion of Series A Preferred Units and Class B units. Under the if-converted method, dilutive convertible securities are assumed to be converted from the date of the issuance, and the resulting common units are included in the denominator of the diluted net income per unit calculation for the period being presented. Each series of potential common units is evaluated in sequence from the most dilutive to the least dilutive. Distributions declared in the period and undeclared distributions on the cumulative Series A Preferred Units that accumulated during the period are added back to the numerator for purposes of the if-converted calculation. As a result of the EQM IDR Transaction, EQM’s common unitholders are entitled to all distributions until the Class B units are converted to common units (other than distributions in respect of the Series A Preferred Units following the initial distribution period for such Series A Preferred Units commencing with the quarter ended June 30, 2019 ). Class B unitholders have no rights to distributions until they are convertible into common units. Accordingly, for all periods prior to the date such Class B units are convertible, the Class B units are not considered participating securities under the two-class method. In addition, the Series A Preferred Units are not considered a participating security as they only have distribution rights up to the specified per-unit quarterly distribution and have no rights to EQM’s undistributed earnings prior to conversion of the Series A Preferred Units into EQM common units, as discussed in Note 5 . For the three and six months ended June 30, 2019 , limited partner interest in net income, which excludes the Series A Preferred Units interest in net income, was fully allocated to EQM’s common unitholders. For the three and six months ended June 30, 2018 , net income attributable to EQM was allocated to the general partner and limited partners in accordance with their respective ownership percentages. Any common units issued during the relevant periods are included on a monthly weighted-average basis for the periods in which they were outstanding. The phantom units granted to the independent and non-employee directors of EQM's general partner will be paid in common units on a director’s termination of service on the Board of Directors of EQM's general partner. The weighted average phantom unit awards included in the calculation of basic weighted average limited partner units outstanding were 24,007 and 21,041 for the three months ended June 30, 2019 and 2018 , respectively, and 22,896 and 20,506 for the six months ended June 30, 2019 and 2018, respectively. The following table presents EQM's calculation of net income per limited partner unit for common and Class B limited partner units. Three Months Ended Six Months Ended 2019 2018 (1) 2019 2018 (1) (Thousands, except per unit data) Net income attributable to EQM $ 152,438 $ 233,832 $ 404,369 $ 494,182 Less: Series A Preferred Units interest in net income (22,979 ) — (22,979 ) — Less: pre-acquisition net income allocated to parent — (72,620 ) — (155,752 ) Less: general partner interest in net income – general partner units — (1,700 ) — (4,791 ) Less: general partner interest in net income – IDRs — (68,121 ) — (112,285 ) Limited partner interest in net income $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to common units $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to Class B units $ — $ — $ — $ — Weighted average limited partner common units outstanding - basic 200,482 83,553 177,498 82,290 Weighted average limited partner common units outstanding - diluted (2) 207,482 83,553 195,645 82,290 Net income per limited partner common unit - basic $ 0.65 $ 1.09 $ 2.15 $ 2.69 Net income per limited partner common unit - diluted $ 0.62 $ 1.09 $ 2.07 $ 2.69 (1) Net income attributable to the Drop-Down Transaction and the EQM-RMP Merger for the periods prior to May 1, 2018 and July 23, 2018, respectively, was not allocated to the limited partners for purposes of calculating net income per limited partner unit as these pre-acquisition amounts were not available to the EQM unitholders. (2) For the three months ended June 30, 2019, 7,000,000 Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. The effect of Series A Preferred Units was anti-dilutive. For the six months ended June 30, 2019, 7,000,000 Class B units and 11,147,148 Series A Preferred Units and Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. Class B units are not a participating security as they do not participate in distributions. Distributions to common unitholders. On July 24, 2019 , the Board of Directors of EQM's general partner declared a cash distribution to EQM's unitholders for the second quarter of 2019 of $1.160 per common unit. The cash distribution will be paid on August 13, 2019 to common unitholders of record at the close of business on August 2, 2019 . Based on the EQM common units outstanding on July 30, 2019 , cash distributions paid by EQM to Equitrans Midstream will be approximately $136.0 million related to Equitrans Midstream's limited partner interest in EQM. Distributions to Series A Preferred Unit holders. On July 24, 2019 , the Board of Directors of EQM's general partner declared a quarterly cash distribution on the Series A Preferred Units for the second quarter of 2019 of $0.9339 per Series A Preferred Unit, which amount reflected pro-ration in accordance with the Fourth Amended and Restated Agreement of Limited Partnership of EQM, dated April 10, 2019. The cash distribution will be paid on August 13, 2019 to Series A Preferred unitholders of record at the close of business on August 2, 2019 . For the quarter ended June 30, 2019 , no distributions were declared on the Class B units as none of these units were convertible into EQM common units.

Financial Statements (Policies)

Financial Statements (Policies)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization EQM is a growth-oriented Delaware limited partnership formed by EQT in January 2012. Prior to the completion of the EQM IDR Transaction (defined below), EQM Midstream Services, LLC was the general partner of EQM (the Former EQM General Partner). Following the consummation of the EQM IDR Transaction, EQGP Services, LLC, a wholly-owned indirect subsidiary of Equitrans Midstream, became the general partner of EQM (the New EQM General Partner). References in these consolidated financial statements to Equitrans Midstream refer collectively to Equitrans Midstream Corporation and its consolidated subsidiaries. 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 operations 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). On November 12, 2018, the Separation was effected through a series of transactions that culminated in EQT's contribution of the Midstream Business to Equitrans Midstream. On February 22, 2019, Equitrans Midstream completed its previously announced simplification transaction pursuant to that certain Agreement and Plan of Merger, dated as of February 13, 2019 (the IDR Merger Agreement), by and among Equitrans Midstream, EQM, the Former EQM General Partner, EQGP, the New EQM General Partner, Equitrans Merger Sub, LP, a Delaware limited partnership (Merger Sub), and certain other parties thereto. Pursuant to the IDR Merger Agreement, on February 22, 2019, (i) Merger Sub merged with and into EQGP (the Merger) with EQGP continuing as the surviving limited partnership and a wholly-owned subsidiary of EQM following the Merger, and (ii) each of (a) the incentive distribution rights (IDRs) in EQM, (b) the economic portion of the general partner interest in EQM and (c) the issued and outstanding common units representing limited partner interests in EQGP were canceled, and, as consideration for such cancellation, certain affiliates of Equitrans Midstream received on a pro rata basis 80,000,000 newly-issued EQM common units and 7,000,000 newly-issued Class B units (Class B units), both representing limited partner interests in EQM, and the New EQM General Partner retained the non-economic general partner interest in EQM (the EQM IDR Transaction). Additionally, as part of the EQM IDR Transaction, the 21,811,643 EQM common units held by EQGP were canceled and 21,811,643 EQM common units were issued pro rata to certain affiliates of Equitrans Midstream. See Note 5 for further information on the EQM IDR Transaction and Class B Units. The EQM IDR Transaction constituted an exchange of equity interests between entities under common control and not a transfer of a business. Therefore, the exchange resulted in a reclassification, as of February 22, 2019, of a $43.8 million deficit capital balance from the general partner line item to the common and Class B line items in EQM's consolidated balance sheets based on the respective limited partner ownership interests. The reclassification represented an allocation of the carrying value of the exchanged general partner interest. Prior to the EQM IDR Transaction, when distributions related to the general partner interest and IDRs were made, earnings equal to the amount of distributions were allocated to the general partner before the remaining earnings were allocated to the limited partner unitholders based on their respective ownership percentages. Subsequent to the EQM IDR Transaction, no earnings will be allocated to the general partner. The allocation of net income attributable to EQM for purposes of calculating net income per limited partner unit is described in Note 12 . On March 13, 2019, EQM entered into a Convertible Preferred Unit Purchase Agreement (inclusive of certain Joinder Agreements entered into on March 18, 2019, the Preferred Unit Purchase Agreement) with certain investors to issue and sell in a private placement (the Private Placement) an aggregate of 24,605,291 Series A Perpetual Convertible Preferred Units (Series A Preferred Units) representing limited partner interests in EQM for a cash purchase price of $48.77 per Series A Preferred Unit, resulting in total gross proceeds of approximately $1.2 billion . The net proceeds from the Private Placement were used in part to fund the purchase price in the Bolt-on Acquisition (defined in Note 2 ) and to pay certain fees and expenses related to the Bolt-on Acquisition, and the remainder was used for general partnership purposes. The Private Placement closed concurrently with the closing of the Bolt-on Acquisition on April 10, 2019 . See Note 5 for further information on the Series A Preferred Units and the Bolt-on Acquisition. Following the EQM IDR Transaction and the closing of the Private Placement, and as of June 30, 2019 , Equitrans Midstream held a 53.5% limited partner interest (after taking into account the Series A Preferred Units issued in the Private Placement on an as-converted basis) and the non-economic general partner interest in EQM. See Note 5 for further information on the EQM IDR Transaction and Private Placement. Basis of Presentation EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions represented business combinations between entities under common control. The recast is for the period the acquired businesses were under the common control of EQT, which began on November 13, 2017 as a result of EQT's acquisition of Rice Energy Inc. (Rice) (the Rice Merger). EQM recorded the assets and liabilities acquired in the Drop-Down Transaction and the EQM-RMP Merger at their carrying amounts to EQT on the effective dates of the transactions. The consolidated financial statements are not necessarily indicative of the actual results of operations if EQM and the assets acquired in the Drop-Down Transaction and the EQM-RMP Merger had been operated together during the pre-acquisition periods. Following the completion of the Bolt-on Acquisition, EQM evaluated Eureka Midstream for consolidation and determined that Eureka Midstream does not meet the criteria for variable interest entity classification due to its ability to independently finance its operations through the Eureka Credit Facility (as defined in Note 10 ), as well as each member having proportional voting rights through their equity investments. As such, as of June 30, 2019 , EQM consolidates Eureka Midstream using the voting interest model, recording noncontrolling interest related to the third-party ownership interests in Eureka Midstream. The accompanying unaudited consolidated financial statements have been prepared in accordance with GAAP for interim financial information and with the requirements of Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these unaudited consolidated financial statements include all adjustments (consisting of only normal recurring adjustments, unless otherwise disclosed in this Form 10-Q) necessary for a fair presentation of the financial position of EQM as of June 30, 2019 and December 31, 2018 , the results of its operations and equity for the three and six months ended June 30, 2019 and 2018 , and its cash flows for the six months ended June 30, 2019 and 2018 . The balance sheet at December 31, 2018 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by GAAP for complete financial statements. Due to the seasonal nature of EQM's utility customer contracts, the interim statements for the three and six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 . EQM does not have any employees. Operational, management and other services for EQM are provided by the directors and officers of the New EQM General Partner and employees of Equitrans Midstream. For further information, refer to the consolidated financial statements and related footnotes for the year ended December 31, 2018, as well as "Management's Discussion and Analysis of Financial Condition and Results of Operations" contained therein.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In February 2016, the FASB issued ASU 2016-02, Leases . The standard requires entities to record assets and obligations for contracts currently recognized as operating leases. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements . The update provides an optional transition method of adoption that permits entities 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. Under the optional transition method, comparative financial information and disclosures are not required. The update also provides transition practical expedients. The standard requires disclosures of the nature, maturity and value of an entity's lease liabilities and elections taken by the entity. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842): Codification Improvements , which, among other things, clarifies interim disclosure requirements in the year of ASU 2016-02 adoption. EQM adopted ASU 2016-02, ASU 2018-11 and ASU 2019-01 on January 1, 2019 using the optional transition method. EQM uses a lease accounting system to monitor its current population of lease contracts. EQM implemented 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. For the disclosures required by the standards, see Note 4 . In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments. The standard amends guidance on reporting credit losses for 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 in current GAAP, and, in its place, requires an entity to recognize its 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. EQM is currently evaluating the effect this standard will have 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. EQM 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. EQM early-adopted the standard using the prospective method of adoption on January 1, 2019. Following the adoption of ASU 2018-15, EQM began capitalizing certain implementation costs related to cloud computing arrangements that are service contracts. The capitalized portion of these costs are included in the property, plant and equipment line on the consolidated balance sheets and will be amortized over the term of EQM's hosting arrangement, which has a fixed term of seven years . For the three and six months ended June 30, 2019 , EQM did no t recognize any amortization expense related to implementation costs on its cloud computing arrangements as such assets were not in use. The costs will be included in the selling, general and administrative expense line on the accompanying statements of consolidated operations when recognized. In August 2018, the U.S. Securities and Exchange Commission (SEC) adopted a final rule under SEC Release No. 33-10532, Disclosure Update and Simplification
Impairment of Long-Lived Assets	EQM evaluates long-lived assets, including related intangibles, for impairment when events or changes in circumstances indicate, in management's judgment, that the carrying value of such assets may not be recoverable. Asset recoverability is measured by comparing the carrying value of the asset or asset group with its expected future pre-tax undiscounted cash flows. These cash flow estimates require EQM to make projections and assumptions for many years into the future for pricing, demand, competition, operating cost and other factors. If the carrying amount exceeds the expected future undiscounted cash flows, EQM recognizes an impairment equal to the excess of net book value over fair value as determined by quoted market prices in active markets or present value techniques if quotes are unavailable. The determination of the fair value using present value techniques requires EQM to make projections and assumptions regarding the probability of a range of outcomes and the rates of interest used in the present value calculations. Any changes EQM makes to these projections and assumptions could result in significant revisions to its evaluation of recoverability of its property, plant and equipment and the recognition of additional impairments.

Acquisitions and Mergers (Table

Acquisitions and Mergers (Tables)	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Schedule Fair Value of Assets Acquired and Liabilities Assumed	The following table summarizes the preliminary allocation of the fair value of the assets and liabilities of the Bolt-on Acquisition as of April 10, 2019 by EQM. (in thousands) Preliminary Purchase Price Allocation Consideration given: Cash consideration $ 861,250 Buyout of Eureka Midstream Class B Units and incentive compensation 2,530 Total consideration 863,780 Fair value of liabilities assumed: Current liabilities 52,458 Long-term debt 300,825 Other long-term liabilities 10,203 Amount attributable to liabilities assumed 363,486 Fair value of assets acquired: Cash 15,145 Accounts receivable 16,817 Inventory 12,991 Other current assets 882 Net property, plant and equipment 1,222,284 Intangible assets 317,000 Other assets 14,567 Amount attributable to assets acquired 1,599,686 Noncontrolling interest (486,062 ) Goodwill $ 113,642 Goodwill and Purchase Price Allocation (Thousands) Estimated fair value of RMP, EQM Olympus, Strike Force (a) and EQM WV $ 4,014,984 Estimated Fair Value of Assets Acquired and Liabilities Assumed: Current assets (b) 132,459 Intangible assets (c) 623,200 Property and equipment, net (d) 2,265,900 Other non-current assets 118 Current liabilities (b) (117,124 ) RMP $850 Million Facility (e) (266,000 ) Other non-current liabilities (e) (9,323 ) Total estimated fair value of assets acquired and liabilities assumed 2,629,230 Goodwill as of November 13, 2017 (f) 1,385,754 Impairment of goodwill (g) 261,941 Goodwill as of December 31, 2018 $ 1,123,813 (a) Includes the estimated fair value attributable to noncontrolling interest of $166 million . (b) The fair value of current assets and current liabilities were assumed to approximate their carrying values. (c) The identifiable intangible assets for customer relationships were estimated by applying a discounted cash flow approach which was adjusted for customer attrition assumptions and projected market conditions. (d) The estimated fair value of long-lived property and equipment were determined utilizing estimated replacement cost adjusted for a usage or obsolescence factor. (e) The estimated fair value of long-term liabilities was determined utilizing observable market inputs where available or estimated based on their then current carrying values. (f) 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. (g) During its annual goodwill assessment for the year ended December 31, 2018, EQM determined that carrying value of the RMP PA Gas Gathering reporting unit, which comprises the Pennsylvania gathering assets acquired in the Rice Merger, was greater than its fair value. As a result, EQM recognized an impairment to goodwill of approximately $261.9 million .
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	Intangible assets, net as of June 30, 2019 are detailed below. (in thousands) As of June 30, 2019 Intangible assets 317,000 Less: accumulated amortization 3,375 Intangible assets, net $ 313,625
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	Unaudited Pro Forma Information. The following unaudited pro forma combined financial information presents EQM's results as though the EQM IDR Transaction and Bolt-on Acquisition had been completed at January 1, 2018. The pro forma combined financial information has been included for comparative purposes and is not necessarily indicative of the results that might have actually occurred had the EQM IDR Transaction and Bolt-on Acquisition taken place on January 1, 2018; furthermore, the financial information is not intended to be a projection of future results. (in thousands, except per unit data)(unaudited) Three Months Ended March 31, 2019 Pro forma operating revenues $ 421,362 Pro forma net income $ 264,215 Pro forma net income attributable to noncontrolling interests $ 3,205 Pro forma net income attributable to EQM $ 261,010 Pro forma income per unit (basic) $ 1.17 Pro forma income per unit (diluted) $ 1.12 (in thousands, except per unit data)(unaudited) Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Pro forma operating revenues $ 406,920 $ 803,945 Pro forma net income $ 242,587 $ 509,403 Pro forma net income attributable to noncontrolling interests $ 4,303 $ 8,710 Pro forma net income attributable to EQM $ 238,284 $ 500,693 Pro forma income per unit (basic) $ 1.06 $ 2.24 Pro forma income per unit (diluted) $ 1.03 $ 2.16 Post-Acquisition Operating Results. Subsequent to the completion of the Bolt-on Acquisition, Eureka Midstream and Hornet Midstream collectively contributed the following to both the Gathering segment and EQM's consolidated operating results for the period from April 10, 2019 through June 30, 2019 . (in thousands)(unaudited) April 10, 2019 through June 30, 2019 Operating revenues $ 28,928 Operating income attributable to EQM $ 12,496 Net income attributable to noncontrolling interests $ 4,033 Net income attributable to EQM $ 6,506

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Schedule of Operating Lease Cost	The following table summarizes operating lease cost for the three and six months ended June 30, 2019 . Three Months Ended June 30, 2019 Six Months Ended (Thousands) Operating lease cost $ 2,852 $ 4,149 Short-term lease cost 1,512 1,880 Variable lease cost 4 12 Total lease cost $ 4,368 $ 6,041
Schedule of Operating Lease Liability Maturities	The following table summarizes undiscounted cash flows owed by EQM to lessors pursuant to contractual agreements in effect as of June 30, 2019 and related imputed interest. The majority of EQM's lease agreements have multiple renewal periods at EQM's option; however, because none of the renewal periods are reasonably assured to be exercised, the associated operating lease payments have not been included in the table below. June 30, 2019 (Thousands) 2019 $ 5,619 2020 10,937 2021 9,161 2022 7,694 2023 5,607 2024 3,966 Thereafter 24,728 Total 67,712 Less: imputed interest 14,597 Present value of operating lease liability $ 53,115

Equity (Tables)

Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Summary of Units Issued	The following table summarizes changes in EQM's Series A Preferred Units, common units and Class B units, each representing limited partner interests in EQM, and general partner units during the year ended December 31, 2018 and from January 1, 2019 through June 30, 2019 . Limited Partner Interests Series A Preferred Units Common Units Class B Units General Partner Units Total Balance at January 1, 2018 — 80,581,758 — 1,443,015 82,024,773 Common units issued (1) — 10,821 — — 10,821 Drop-Down Transaction consideration — 5,889,282 — — 5,889,282 Common units issued in the EQM-RMP Merger — 33,975,777 — — 33,975,777 Balance at December 31, 2018 — 120,457,638 — 1,443,015 121,900,653 Unit cancellation — (8 ) — — (8 ) EQM IDR Transaction (2) — 80,000,000 7,000,000 (1,443,015 ) 85,556,985 Issuance of Series A Preferred Units 24,605,291 — — — 24,605,291 Balance at June 30, 2019 24,605,291 200,457,630 7,000,000 — 232,062,921 (1) Units issued upon the resignation of a member of the Board of Directors of EQM's general partner. (2) In exchange for the cancellation of the EQM IDRs, EQM issued 87,000,000 EQM common units (the Exchange Consideration) to the Former EQM General Partner. At the effective time of the EQM IDR Merger, (i) the Exchange Consideration held by the Former EQM General Partner was canceled, (ii) 80,000,000 EQM common units and 7,000,000 Class B units were issued on a pro rata basis to certain affiliates of Equitrans Midstream, and (iii) 21,811,643 EQM common units held by EQGP were canceled and 21,811,643 EQM common units were issued pro rata to certain affiliates of Equitrans Midstream.

Financial Information by Busi_2

Financial Information by Business Segment (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Operating Income and Reconciliation to Net Income	Three Months Ended Six Months Ended 2019 2018 2019 2018 (Thousands) Revenues from customers (including related parties): Gathering $ 285,666 $ 241,189 $ 547,547 $ 478,579 Transmission 92,767 89,145 202,626 196,079 Water 27,734 44,363 45,776 71,065 Total operating revenues $ 406,167 $ 374,697 $ 795,949 $ 745,723 Operating income: Gathering $ 94,131 $ 161,818 $ 276,209 $ 332,853 Transmission 63,244 60,642 147,994 140,093 Water 10,072 23,408 11,258 38,720 Total operating income $ 167,447 $ 245,868 $ 435,461 $ 511,666 Reconciliation of operating income to net income: Equity income (a) $ 36,782 $ 10,938 $ 67,845 $ 19,749 Other income 1,959 944 4,169 1,848 Net interest expense 49,717 23,065 99,073 35,735 Net income $ 156,471 $ 234,685 $ 408,402 $ 497,528 (a) Equity income is included in the Transmission segment.
Schedule of Segment Assets	June 30, December 31, (Thousands) Segment assets: Gathering $ 8,031,401 $ 6,011,654 Transmission (a) 3,636,355 3,066,659 Water 262,773 237,602 Total operating segments 11,930,529 9,315,915 Headquarters, including cash 132,641 140,206 Total assets $ 12,063,170 $ 9,456,121 (a) The equity investment in the MVP Joint Venture is included in the Transmission segment.
Schedule of Depreciation, Amortization, and Expenditures for Segment Assets	Three Months Ended Six Months Ended 2019 2018 2019 2018 (Thousands) Depreciation: Gathering $ 37,443 $ 23,882 $ 65,559 $ 46,950 Transmission 12,594 12,430 25,127 24,871 Water 6,478 5,798 12,894 11,569 Total $ 56,515 $ 42,110 $ 103,580 $ 83,390 Expenditures for segment assets: Gathering (1)(2) $ 265,198 $ 186,457 $ 472,915 $ 320,595 Transmission (3) 11,229 27,962 29,991 46,891 Water 8,849 7,002 18,024 9,377 Total (4) $ 285,276 $ 221,421 $ 520,930 $ 376,863 (1) Includes approximately $8.9 million and $58.6 million for the three and six months ended June 30, 2019 , respectively, related to non-operating assets acquired from Equitrans Midstream in the Shared Assets Transaction that primarily support EQM's gathering activities. (2) Includes approximately $10.9 million of capital expenditures related to noncontrolling interests in Eureka Midstream for the three and six months ended June 30, 2019 . (3) Transmission capital expenditures do not include capital contributions made to the MVP Joint Venture for the MVP and MVP Southgate projects of approximately $156.4 million and $65.8 million for the three months ended June 30, 2019 and 2018 , respectively, and approximately $301.2 million and $182.8 million for the six months ended June 30, 2019 and 2018 , respectively. (4) EQM accrues capital expenditures when work has been completed but the associated bills have not yet been paid. These accrued amounts are excluded from capital expenditures in the statements of consolidated cash flows until they are paid. Accrued capital expenditures were approximately $110.8 million , $137.8 million and $108.9 million at June 30, 2019 , March 31, 2019 and December 31, 2018 , respectively. Accrued capital expenditures were approximately $84.6 million , $75.5 million and $90.7 million at June 30, 2018 , March 31, 2018 and December 31, 2017 , respectively. On April 10, 2019, as a result of the Bolt-on Acquisition, EQM assumed $8.8 million of Eureka Midstream accrued capital expenditures.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregated Revenue Information, by Business Segment	The tables below provide disaggregated revenue information by business segment. Three Months Ended June 30, 2019 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 147,771 $ 81,836 $ — $ 229,607 Volumetric-based fee revenues 137,895 10,931 — 148,826 Water services revenues — — 27,734 27,734 Total operating revenues $ 285,666 $ 92,767 $ 27,734 $ 406,167 Three Months Ended June 30, 2018 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 111,702 $ 82,222 $ — $ 193,924 Volumetric-based fee revenues 129,487 6,923 — 136,410 Water services revenues — — 44,363 44,363 Total operating revenues $ 241,189 $ 89,145 $ 44,363 $ 374,697 Six Months Ended June 30, 2019 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 276,730 $ 181,060 $ — $ 457,790 Volumetric-based fee revenues 270,817 21,566 — 292,383 Water service revenues — — 45,776 45,776 Total operating revenues $ 547,547 $ 202,626 $ 45,776 $ 795,949 Six Months Ended June 30, 2018 Gathering Transmission Water Total (Thousands) Firm reservation fee revenues $ 221,635 $ 179,997 $ — $ 401,632 Volumetric-based fee revenues 256,944 16,082 — 273,026 Water service revenues — — 71,065 71,065 Total operating revenues $ 478,579 $ 196,079 $ 71,065 $ 745,723
Summary of Remaining Performance Obligations	The following table summarizes the transaction price allocated to EQM's remaining performance obligations under all contracts with firm reservation fees and minimum volume commitments (MVCs) as of June 30, 2019 . 2019 (a) 2020 2021 2022 2023 Thereafter Total (Thousands) Gathering firm reservation fees $ 253,531 $ 566,813 $ 614,356 $ 614,356 $ 614,264 $ 2,647,183 $ 5,310,503 Gathering revenues supported by MVCs 45,877 95,294 100,715 100,715 100,715 309,214 752,530 Transmission firm reservation fees 163,370 334,627 345,527 340,453 336,333 2,478,310 3,998,620 Total $ 462,778 $ 996,734 $ 1,060,598 $ 1,055,524 $ 1,051,312 $ 5,434,707 $ 10,061,653 (a)

Investment in Unconsolidated _2

Investment in Unconsolidated Entity (Tables)	6 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Unaudited Condensed Financial Statements for the Investment in Unconsolidated Equity	The following tables summarize the unaudited condensed consolidated financial statements of the MVP Joint Venture. Condensed Consolidated Balance Sheets June 30, December 31, (Thousands) Current assets $ 836,397 $ 687,657 Non-current assets 4,033,475 3,223,220 Total assets $ 4,869,872 $ 3,910,877 Current liabilities $ 420,534 $ 617,355 Non-current liabilities 2,166 — Equity 4,447,172 3,293,522 Total liabilities and equity $ 4,869,872 $ 3,910,877 Condensed Statements of Consolidated Operations Three Months Ended Six Months Ended 2019 2018 2019 2018 (Thousands) Environmental remediation reserve $ 26 $ — $ (2,166 ) $ — Other income 1,785 743 4,698 1,277 Net interest income 23,700 6,989 43,935 12,638 AFUDC - equity 55,298 16,307 102,514 29,489 Net income $ 80,809 $ 24,039 $ 148,981 $ 43,404

Net Income per Limited Partne_2

Net Income per Limited Partner Unit and Cash Distributions (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Diluted	The following table presents EQM's calculation of net income per limited partner unit for common and Class B limited partner units. Three Months Ended Six Months Ended 2019 2018 (1) 2019 2018 (1) (Thousands, except per unit data) Net income attributable to EQM $ 152,438 $ 233,832 $ 404,369 $ 494,182 Less: Series A Preferred Units interest in net income (22,979 ) — (22,979 ) — Less: pre-acquisition net income allocated to parent — (72,620 ) — (155,752 ) Less: general partner interest in net income – general partner units — (1,700 ) — (4,791 ) Less: general partner interest in net income – IDRs — (68,121 ) — (112,285 ) Limited partner interest in net income $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to common units $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to Class B units $ — $ — $ — $ — Weighted average limited partner common units outstanding - basic 200,482 83,553 177,498 82,290 Weighted average limited partner common units outstanding - diluted (2) 207,482 83,553 195,645 82,290 Net income per limited partner common unit - basic $ 0.65 $ 1.09 $ 2.15 $ 2.69 Net income per limited partner common unit - diluted $ 0.62 $ 1.09 $ 2.07 $ 2.69 (1) Net income attributable to the Drop-Down Transaction and the EQM-RMP Merger for the periods prior to May 1, 2018 and July 23, 2018, respectively, was not allocated to the limited partners for purposes of calculating net income per limited partner unit as these pre-acquisition amounts were not available to the EQM unitholders. (2) For the three months ended June 30, 2019, 7,000,000 Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. The effect of Series A Preferred Units was anti-dilutive. For the six months ended June 30, 2019, 7,000,000 Class B units and 11,147,148 Series A Preferred Units and Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. Class B units are not a participating security as they do not participate in distributions.
Schedule of Earnings Per Share, Basic	The following table presents EQM's calculation of net income per limited partner unit for common and Class B limited partner units. Three Months Ended Six Months Ended 2019 2018 (1) 2019 2018 (1) (Thousands, except per unit data) Net income attributable to EQM $ 152,438 $ 233,832 $ 404,369 $ 494,182 Less: Series A Preferred Units interest in net income (22,979 ) — (22,979 ) — Less: pre-acquisition net income allocated to parent — (72,620 ) — (155,752 ) Less: general partner interest in net income – general partner units — (1,700 ) — (4,791 ) Less: general partner interest in net income – IDRs — (68,121 ) — (112,285 ) Limited partner interest in net income $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to common units $ 129,459 $ 91,391 $ 381,390 $ 221,354 Net income allocable to Class B units $ — $ — $ — $ — Weighted average limited partner common units outstanding - basic 200,482 83,553 177,498 82,290 Weighted average limited partner common units outstanding - diluted (2) 207,482 83,553 195,645 82,290 Net income per limited partner common unit - basic $ 0.65 $ 1.09 $ 2.15 $ 2.69 Net income per limited partner common unit - diluted $ 0.62 $ 1.09 $ 2.07 $ 2.69 (1) Net income attributable to the Drop-Down Transaction and the EQM-RMP Merger for the periods prior to May 1, 2018 and July 23, 2018, respectively, was not allocated to the limited partners for purposes of calculating net income per limited partner unit as these pre-acquisition amounts were not available to the EQM unitholders. (2) For the three months ended June 30, 2019, 7,000,000 Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. The effect of Series A Preferred Units was anti-dilutive. For the six months ended June 30, 2019, 7,000,000 Class B units and 11,147,148 Series A Preferred Units and Class B units were included in the calculation of diluted weighted average limited partner units outstanding based upon the application of the if-converted method. Class B units are not a participating security as they do not participate in distributions.

Financial Statements (Details)

Financial Statements (Details) - USD ($)		Mar. 13, 2019	Feb. 22, 2019	Feb. 13, 2019	Feb. 28, 2019	Jun. 30, 2019	Mar. 31, 2019		Jun. 30, 2019	Dec. 31, 2018
Cloud Computing Arrangements
Class of Stock [Line Items]
Useful life									7 years
Amortization expense related to implementation costs						$ 0			$ 0
Common Units
Class of Stock [Line Items]
Canceled common units (in shares)				21,811,643
General Partner
Class of Stock [Line Items]
Exchange of equity interests			$ (43,800,000)				$ (43,782,000)	[1]
EQM | Common Units | EQGP
Class of Stock [Line Items]
Partners' capital common units outstanding (in shares)				21,811,643		21,811,643			21,811,643
EQM | Common Units | Equitrans Midstream Holdings, LLC
Class of Stock [Line Items]
Limited partner ownership interest (as a percent)									53.50%
Class B Units
Class of Stock [Line Items]
Canceled common units (in shares)						7,000,000			7,000,000	0
Class B Units | Common Units
Class of Stock [Line Items]
Exchange of equity interests	[1]						$ 1,477,000
IDR Merger Agreement
Class of Stock [Line Items]
Newly-issued common units (in shares)				80,000,000					80,000,000
IDR Merger Agreement | Class B Units
Class of Stock [Line Items]
Newly-issued common units (in shares)				7,000,000	7,000,000				7,000,000
Private Placement
Class of Stock [Line Items]
Aggregate number of units owned (in shares)		24,605,291							24,605,291
Cash purchase price for Series A Preferred Units (in dollars per share)		$ 48.77
Consideration received on transaction		$ 1,200,000,000
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.

Acquisitions and Mergers - Narr

Acquisitions and Mergers - Narrative (Details)		Apr. 10, 2019USD ($)mi	Mar. 31, 2019USD ($)	May 01, 2018USD ($)shares	Apr. 25, 2018USD ($)reporting_unitshares	Nov. 13, 2017USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)		Jun. 30, 2018USD ($)		Dec. 31, 2018USD ($)	Nov. 01, 2018USD ($)
Business Acquisition [Line Items]
Limited partner ownership interest (as a percent)								25.00%			25.00%
Payment of related interest and fees									$ 28,325,000		$ 0
Interest, net of amount capitalized	[1]								106,001,000		33,621,000
Separation and other transaction costs	[2]						$ 15,358,000	$ 5,350,000	18,871,000		5,350,000
Goodwill							1,237,456,000		1,237,456,000				$ 1,123,813,000
Amortization of intangible assets	[2]						13,750,000	$ 10,387,000	24,137,000	[1]	$ 20,773,000	[1]
Estimated annual amortization expense, 2023							15,800,000		15,800,000
Purchase of assets			$ 49,700,000				8,900,000
Number of reporting units | reporting_unit					2
EQM Credit Facility | Line of credit
Business Acquisition [Line Items]
Credit facility														$ 3,000,000,000
Strike Force Midstream
Business Acquisition [Line Items]
Ownership interest (as a percent)				100.00%
Bolt-on Acquisition
Business Acquisition [Line Items]
Total consideration		$ 1,030,000,000
Cash consideration		863,780,000
Assumed pro-rata debt		167,000,000
Separation and other transaction costs							15,200,000		16,700,000
Acquisition-related expenses							13,500,000		15,000,000
Acquisition-related expenses, professional fees							1,700,000		1,700,000
Goodwill		113,642,000
Non-controlling interest acquired, fair value		$ 486,062,000
Estimated useful life		20 years
Amortization of intangible assets							3,400,000		3,400,000
Estimated annual amortization expense, 2019							8,100,000		8,100,000
Estimated annual amortization expense, 2020							15,800,000		15,800,000
Estimated annual amortization expense, 2021							15,800,000		15,800,000
Estimated annual amortization expense, 2022							$ 15,800,000		$ 15,800,000
Eureka Midstream Holdings, LLC
Business Acquisition [Line Items]
Limited partner ownership interest (as a percent)		60.00%
Length of gathering lines (in miles) | mi		190
Hornet Midstream Holdings, LLC
Business Acquisition [Line Items]
Limited partner ownership interest (as a percent)		100.00%
Length of gathering lines (in miles) | mi		15
Payment of related interest and fees		$ 28,200,000
Interest, net of amount capitalized		$ 100,000
EQM-RMP Merger
Business Acquisition [Line Items]
Total consideration						$ 4,014,984,000
Goodwill						1,385,754,000							$ 1,123,813,000
Non-controlling interest acquired, fair value						166,000,000
EQM-RMP Merger | Rice Midstream Partners, LP
Business Acquisition [Line Items]
Common share conversation ratio					0.3319
Equity interest issued or issuable (in shares) | shares					34,000,000
EQM-RMP Merger | EQT
Business Acquisition [Line Items]
Measurement period adjustments increasing goodwill						$ 900,000
EQM-RMP Merger | EQM | EQT
Business Acquisition [Line Items]
Equity interest issued or issuable (in shares) | shares					9,544,530
May 2018 Acquisition
Business Acquisition [Line Items]
Cash consideration				$ 1,150,000,000
Equity interest issued or issuable (in shares) | shares				5,889,282
May 2018 Acquisition | Strike Force Midstream | Strike Force Midstream Holdings LLC
Business Acquisition [Line Items]
Ownership interest (as a percent)				75.00%
EQM-RMP Merger and Drop-Down Transaction
Business Acquisition [Line Items]
Goodwill					$ 1,384,900,000
Strike Force Midstream
Business Acquisition [Line Items]
Limited partner ownership interest (as a percent)				25.00%
Total consideration				$ 175,000,000
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.
[2]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.

Acquisitions and Mergers - Sche

Acquisitions and Mergers - Schedule Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Apr. 10, 2019	Dec. 31, 2018	Dec. 31, 2018	Jun. 30, 2019	Nov. 13, 2017
Fair value of assets acquired:
Goodwill		$ 1,123,813	$ 1,123,813	$ 1,237,456
Bolt-on Acquisition
Consideration given:
Cash consideration	$ 861,250
Buyout of Eureka Midstream Class B Units and incentive compensation	2,530
Total consideration	863,780
Fair value of liabilities assumed:
Current liabilities	(52,458)
Long-term debt	300,825
Other long-term liabilities	10,203
Amount attributable to liabilities assumed	363,486
Fair value of assets acquired:
Cash	15,145
Accounts receivable	16,817
Inventory	12,991
Other current assets	882
Net property, plant and equipment	1,222,284
Other assets	14,567
Intangible assets	317,000
Amount attributable to assets acquired	1,599,686
Noncontrolling interest	(486,062)
Goodwill	$ 113,642
EQM-RMP Merger
Fair value of liabilities assumed:
Current liabilities					$ (117,124)
Long-term debt					266,000
Other long-term liabilities					9,323
Fair value of assets acquired:
Other current assets					132,459
Net property, plant and equipment					2,265,900
Other assets					118
Intangible assets					623,200
Noncontrolling interest					(166,000)
Goodwill		1,123,813	1,123,813		1,385,754
Total estimated fair value of assets acquired and liabilities assumed					$ 2,629,230
Impairment of goodwill		$ 261,900	$ 261,941

Acquisitions and Mergers - Sc_2

Acquisitions and Mergers - Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination (Details) - Bolt-on Acquisition $ in Thousands	Jun. 30, 2019USD ($)
Business Acquisition [Line Items]
Intangible assets	$ 317,000
Less: accumulated amortization	3,375
Intangible assets, net	$ 313,625

Acquisitions and Mergers - Sc_3

Acquisitions and Mergers - Schedule of Post-Acquisition Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2019	[1]	Jun. 30, 2019	Jun. 30, 2018	[1]	Jun. 30, 2019	[1]	Jun. 30, 2018	[1]
Business Acquisition [Line Items]
Net income attributable to noncontrolling interests	$ 4,033		$ 4,033	$ 853		$ 4,033		$ 3,346
Net income attributable to EQM	$ 152,438		6,506	$ 233,832		$ 404,369		$ 494,182
Bolt-on Acquisition
Business Acquisition [Line Items]
Operating revenues			28,928
Operating income attributable to EQM			$ 12,496
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.

Acquisitions and Mergers - Sc_4

Acquisitions and Mergers - Schedule of Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2018
Business Combinations [Abstract]
Pro forma operating revenues	$ 421,362	$ 406,920	$ 803,945
Pro forma net income	264,215	242,587	509,403
Pro forma net income attributable to noncontrolling interests	3,205	4,303	8,710
Pro forma net income attributable to EQM	$ 261,010	$ 238,284	$ 500,693
Pro forma income per unit (basic) (USD per share)	$ 1.17	$ 1.06	$ 2.24
Pro forma income per unit (diluted) (USD per share)	$ 1.12	$ 1.03	$ 2.16

Impairment of Long-Lived Asse_2

Impairment of Long-Lived Assets (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018
Property, Plant and Equipment [Abstract]
Impairment of certain non-core natural gas pipeline assets	[1],[2]	$ 80,135	$ 0	$ 80,135	[3]	$ 0	[3]
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	See Note 3 for disclosure regarding impairment of certain of EQM's long-lived assets.
[3]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands	Apr. 10, 2019USD ($)lease_agreement	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)lease_agreement	Jun. 30, 2019USD ($)	Jan. 01, 2019USD ($)
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use asset		$ 52,800		$ 52,800
Operating lease, liability		53,115		53,115
Operating lease cost		2,852		4,149
Cash paid for operating lease liabilities		2,500		3,800
Operating lease, liability, current		$ 8,800		$ 8,800
Weighted average remaining lease term		8 years		8 years
Weighted average discount rate (percentage)		6.00%		6.00%
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use asset					$ 2,300
Operating lease, liability					$ 2,300
Shared Leases Assignment
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use asset			$ 33,000
Operating lease, liability			$ 33,000
Number leases | lease_agreement			2
Bolt-on Acquisition
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use asset	$ 20,000
Operating lease, liability	$ 20,000
Operating lease cost		$ 1,300		$ 1,300
Bolt-on Acquisition | Compressor Lease
Lessee, Lease, Description [Line Items]
Number leases | lease_agreement	10
Bolt-on Acquisition | Facilities Lease
Lessee, Lease, Description [Line Items]
Number leases | lease_agreement	1

Leases - Schedule of Operating

Leases - Schedule of Operating Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 2,852	$ 4,149
Short-term lease cost	1,512	1,880
Variable lease cost	4	12
Total lease cost	$ 4,368	$ 6,041

Leases - Schedule of Operatin_2

Leases - Schedule of Operating Lease Liability Maturities (Details) $ in Thousands	Jun. 30, 2019USD ($)
Leases [Abstract]
2019	$ 5,619
2020	10,937
2021	9,161
2022	7,694
2023	5,607
2024	3,966
Thereafter	24,728
Total	67,712
Less: imputed interest	14,597
Present value of operating lease liability	$ 53,115

Equity - Summary of Units Issue

Equity - Summary of Units Issued (Details) - shares	Feb. 13, 2019	Feb. 28, 2019	Jun. 30, 2019	Dec. 31, 2018
Increase (Decrease) in Partners' Capital
Balance at beginning (in shares)			121,900,653	82,024,773
Units issued in the period (in shares)			24,605,291	10,821
Unit cancellation (in shares)			(8)
EQM IDR Transaction (in shares)			85,556,985
Balance at end (in shares)			232,062,921	121,900,653
IDR Merger Agreement
Increase (Decrease) in Partners' Capital
Newly-issued common units (in shares)	80,000,000		80,000,000
Class B Units | IDR Merger Agreement
Increase (Decrease) in Partners' Capital
Newly-issued common units (in shares)	7,000,000	7,000,000	7,000,000
Drop Down Transaction
Increase (Decrease) in Partners' Capital
Units issued in Drop-Down and Merger transactions (in shares)				5,889,282
EQM-RMP Merger
Increase (Decrease) in Partners' Capital
Units issued in Drop-Down and Merger transactions (in shares)				33,975,777
Limited Partner Interests | Series A Preferred Units
Increase (Decrease) in Partners' Capital
Units issued in the period (in shares)			24,605,291
Balance at end (in shares)			24,605,291
Limited Partner Interests | Common Units
Increase (Decrease) in Partners' Capital
Balance at beginning (in shares)			120,457,638	80,581,758
Units issued in the period (in shares)				10,821
Unit cancellation (in shares)			(8)
EQM IDR Transaction (in shares)			80,000,000
Balance at end (in shares)			200,457,630	120,457,638
Limited Partner Interests | Class B Units
Increase (Decrease) in Partners' Capital
EQM IDR Transaction (in shares)			7,000,000
Balance at end (in shares)			7,000,000
Limited Partner Interests | Drop Down Transaction | Common Units
Increase (Decrease) in Partners' Capital
Units issued in Drop-Down and Merger transactions (in shares)				5,889,282
Limited Partner Interests | EQM-RMP Merger | Common Units
Increase (Decrease) in Partners' Capital
Units issued in Drop-Down and Merger transactions (in shares)				33,975,777
General Partner Units
Increase (Decrease) in Partners' Capital
Balance at beginning (in shares)			1,443,015	1,443,015
EQM IDR Transaction (in shares)			(1,443,015)
Balance at end (in shares)			0	1,443,015
General Partner Units | Common Units
Increase (Decrease) in Partners' Capital
EQM IDR Transaction (in shares)			87,000,000
Common Units
Increase (Decrease) in Partners' Capital
EQM IDR Transaction (in shares)			21,811,643
Common Units | EQM | EQGP
Increase (Decrease) in Partners' Capital
Partners' capital common units outstanding (in shares)	21,811,643		21,811,643

Equity - Narrative (Details)

Equity - Narrative (Details)	Mar. 13, 2019USD ($)day$ / sharesshares	Feb. 13, 2019shares	Feb. 28, 2019USD ($)shares	Jun. 30, 2019$ / sharesshares	Mar. 31, 2019$ / shares	Jun. 30, 2018$ / shares	Mar. 31, 2018$ / shares	Jun. 30, 2019shares	Dec. 31, 2018shares
Class of Stock [Line Items]
Distributions paid to unitholders (dollars per common unit) | $ / shares				$ 1.145	$ 1.13	$ 1.065	$ 1.025
Conversion basis	100.00%
Convertible units | $	$ 30,000,000
Threshold percentage of stock price trigger	140.00%
Threshold trading days | day	20
Threshold amount of stock price trigger (in shares)	500,000
Threshold consecutive trading days | day	20
Private Placement
Class of Stock [Line Items]
Aggregate number of units owned (in shares)	24,605,291							24,605,291
Cash purchase price for Series A Preferred Units (in dollars per share) | $ / shares	$ 48.77
Consideration received on transaction | $	$ 1,200,000,000
Distributions paid to unitholders (dollars per common unit) | $ / shares	$ 1.0364
Cumulative quarterly distribution increasing percentage (B)	1.725%
IDR Merger Agreement
Class of Stock [Line Items]
Common units received (in shares)		80,000,000						80,000,000
Units convertible as of April 1, 2021 | $			$ 2,500,000
Units convertible as of April 1, 2022 | $			2,500,000
Units convertible as of April 1, 2023 | $			$ 2,000,000
Class B Units
Class of Stock [Line Items]
Common units outstanding (in shares)				7,000,000				7,000,000	0
Class B Units | IDR Merger Agreement
Class of Stock [Line Items]
Common units received (in shares)		7,000,000	7,000,000					7,000,000
ETRN | Class B Units
Class of Stock [Line Items]
Common units outstanding (in shares)				7,000,000				7,000,000
EQM | Private Placement
Class of Stock [Line Items]
Cash purchase price for Series A Preferred Units (in dollars per share) | $ / shares	$ 48.77
Cumulative quarterly distribution increasing percentage (A)	2.59%
Cumulative quarterly distribution increasing percentage (B)	6.90%
EQM | Public Ownership Interest
Class of Stock [Line Items]
Limited partner ownership interest (as a percent)								46.50%
EQM | Common Units | Equitrans Gathering Holdings, LLC
Class of Stock [Line Items]
Common units outstanding (in shares)				89,505,616				89,505,616
EQM | Common Units | Equitrans Gathering Holdings, LLC | Class B Units
Class of Stock [Line Items]
Common units outstanding (in shares)				6,153,907				6,153,907
EQM | Common Units | EQM GP Corporation
Class of Stock [Line Items]
Common units outstanding (in shares)				89,536				89,536
EQM | Common Units | EQM GP Corporation | Class B Units
Class of Stock [Line Items]
Common units outstanding (in shares)				6,155				6,155
EQM | Common Units | Equitrans Midstream Holdings, LLC
Class of Stock [Line Items]
Common units outstanding (in shares)				27,650,303				27,650,303
Limited partner ownership interest (as a percent)								53.50%
EQM | Common Units | Equitrans Midstream Holdings, LLC | Class B Units
Class of Stock [Line Items]
Common units outstanding (in shares)				839,938				839,938
EQM | Common Units | ETRN
Class of Stock [Line Items]
Common units outstanding (in shares)				117,245,455				117,245,455
Limited partner ownership interest (as a percent)								53.50%

Financial Information by Busi_3

Financial Information by Business Segment - Narrative (Details)	6 Months Ended
	Jun. 30, 2019business_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		3 Months Ended						6 Months Ended
		Jun. 30, 2019		Mar. 31, 2019	Jun. 30, 2018		Mar. 31, 2018	Jun. 30, 2019		Jun. 30, 2018		Apr. 10, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from customers (including related parties):
Total operating revenues	[1],[2]	$ 406,167			$ 374,697			$ 795,949		$ 745,723
Operating income:
Total operating income	[1]	167,447			245,868			435,461		511,666
Reconciliation of operating income to net income:
Equity income	[1],[3]	36,782			10,938			67,845	[4]	19,749	[4]
Other income	[1]	1,959			944			4,169		1,848
Net interest expense	[1],[5]	49,717			23,065			99,073		35,735
Net income	[4]	156,471	[1]	$ 251,931	234,685	[1]	$ 262,843	408,402	[1]	497,528	[1]
Segment assets:
Total assets		12,063,170						12,063,170					$ 9,456,121
Depreciation:
Depreciation	[1]	56,515			42,110			103,580	[4]	83,390	[4]
Expenditures for segment assets:
Accrued capital expenditures		110,800		$ 137,800	84,600		$ 75,500	110,800		84,600			108,900	$ 90,700
Operating Segments
Segment assets:
Total assets		11,930,529						11,930,529					9,315,915
Depreciation:
Depreciation		56,515			42,110			103,580		83,390
Expenditures for segment assets:
Expenditures for segment assets		285,276			221,421			520,930		376,863
Headquarters, including cash
Segment assets:
Total assets		132,641						132,641					140,206
Gathering
Revenues from customers (including related parties):
Total operating revenues		285,666			241,189			547,547		478,579
Gathering | Operating Segments
Revenues from customers (including related parties):
Total operating revenues		285,666			241,189			547,547		478,579
Operating income:
Total operating income		94,131			161,818			276,209		332,853
Segment assets:
Total assets		8,031,401						8,031,401					6,011,654
Depreciation:
Depreciation		37,443			23,882			65,559		46,950
Expenditures for segment assets:
Expenditures for segment assets		265,198			186,457			472,915		320,595
Transmission
Revenues from customers (including related parties):
Total operating revenues		92,767			89,145			202,626		196,079
Transmission | Operating Segments
Revenues from customers (including related parties):
Total operating revenues		92,767			89,145			202,626		196,079
Operating income:
Total operating income		63,244			60,642			147,994		140,093
Segment assets:
Total assets		3,636,355						3,636,355					3,066,659
Depreciation:
Depreciation		12,594			12,430			25,127		24,871
Expenditures for segment assets:
Expenditures for segment assets		11,229			27,962			29,991		46,891
Water
Revenues from customers (including related parties):
Total operating revenues		27,734			44,363			45,776		71,065
Water | Operating Segments
Revenues from customers (including related parties):
Total operating revenues		27,734			44,363			45,776		71,065
Operating income:
Total operating income		10,072			23,408			11,258		38,720
Segment assets:
Total assets		262,773						262,773					$ 237,602
Depreciation:
Depreciation		6,478			5,798			12,894		11,569
Expenditures for segment assets:
Expenditures for segment assets		8,849			7,002			18,024		9,377
ETRN | Gathering | Operating Segments
Expenditures for segment assets:
Expenditures for segment assets		8,900						58,600
Eureka Midstream Holdings, LLC | Gathering | Operating Segments
Expenditures for segment assets:
Expenditures for segment assets		10,900						10,900
Bolt-on Acquisition
Expenditures for segment assets:
Accrued capital expenditures												$ 8,800
MVP Joint Venture | Transmission | Operating Segments
Expenditures for segment assets:
Expenditures for segment assets		$ 156,400			$ 65,800			$ 301,200		$ 182,800
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of $284.0 million and $285.3 million for the three months ended June 30, 2019 and 2018 , respectively, and $568.5 million and $550.9 million for the six months ended June 30, 2019 , respectively. See Note 8 .
[3]	Represents equity income from Mountain Valley Pipeline, LLC (the MVP Joint Venture). See Note 9 .
[4]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.
[5]	Net interest expense included interest income on the Preferred Interest in EQT Energy Supply, LLC (EES) of $1.6 million and $1.7 million for the three months ended June 30, 2019 and 2018 , respectively, and $3.2 million and $3.3 million for the six months ended June 30, 2019 and 2018 , respectively.

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Schedule of Disaggregated Revenue Information, by Business Segment (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total operating revenues	[1],[2]	$ 406,167	$ 374,697	$ 795,949	$ 745,723
Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		229,607	193,924	457,790	401,632
Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		148,826	136,410	292,383	273,026
Gathering
Disaggregation of Revenue [Line Items]
Total operating revenues		285,666	241,189	547,547	478,579
Gathering | Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		147,771	111,702	276,730	221,635
Gathering | Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		137,895	129,487	270,817	256,944
Transmission
Disaggregation of Revenue [Line Items]
Total operating revenues		92,767	89,145	202,626	196,079
Transmission | Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		81,836	82,222	181,060	179,997
Transmission | Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		10,931	6,923	21,566	16,082
Water
Disaggregation of Revenue [Line Items]
Total operating revenues		27,734	44,363	45,776	71,065
Water | Firm reservation fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		0	0	0	0
Water | Volumetric-based fee revenues
Disaggregation of Revenue [Line Items]
Total operating revenues		$ 0	$ 0	$ 0	$ 0
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	Operating revenues included related party revenues from EQT Corporation (NYSE: EQT) (EQT) of $284.0 million and $285.3 million for the three months ended June 30, 2019 and 2018 , respectively, and $568.5 million and $550.9 million for the six months ended June 30, 2019 , respectively. See Note 8 .

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Summary of Remaining Performance Obligations (Details) $ in Thousands	Jun. 30, 2019USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	$ 462,778
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	996,734
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	1,060,598
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	1,055,524
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	1,051,312
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	5,434,707
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	10,061,653
Transmission | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	$ 163,370
Remaining performance obligations, expected timing	6 months
Transmission | 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	$ 334,627
Remaining performance obligations, expected timing	1 year
Transmission | 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	$ 345,527
Remaining performance obligations, expected timing	1 year
Transmission | 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	$ 340,453
Remaining performance obligations, expected timing	1 year
Transmission | 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	$ 336,333
Remaining performance obligations, expected timing	1 year
Transmission | 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	$ 2,478,310
Remaining performance obligations, expected timing
Transmission | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	$ 3,998,620
Gathering firm reservation fees | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	$ 253,531
Remaining performance obligations, expected timing	6 months
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	$ 566,813
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	$ 614,356
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	$ 614,356
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	$ 614,264
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	$ 2,647,183
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	$ 5,310,503
Minimum volume commitment contract | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	$ 45,877
Remaining performance obligations, expected timing	6 months
Minimum volume commitment contract | 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	$ 95,294
Remaining performance obligations, expected timing	1 year
Minimum volume commitment contract | 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	$ 100,715
Remaining performance obligations, expected timing	1 year
Minimum volume commitment contract | 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	$ 100,715
Remaining performance obligations, expected timing	1 year
Minimum volume commitment contract | 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	$ 100,715
Remaining performance obligations, expected timing	1 year
Minimum volume commitment contract | 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	$ 309,214
Remaining performance obligations, expected timing
Minimum volume commitment contract | Gathering | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total	$ 752,530

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Narrative (Details)	6 Months Ended
	Jun. 30, 2019
Gathering
Disaggregation of Revenue [Line Items]
Weighted average remaining term	11 years
Transmission
Disaggregation of Revenue [Line Items]
Weighted average remaining term	15 years

Related Party Transactions (Det

Related Party Transactions (Details)	Jun. 30, 2019
EQT | Equitrans Midstream Holdings, LLC
Related Party Transaction [Line Items]
Ownership interest	19.90%

Investment in Unconsolidated _3

Investment in Unconsolidated Entity - Narrative (Details) $ in Millions	1 Months Ended				6 Months Ended
	Sep. 30, 2019USD ($)	Aug. 31, 2019USD ($)	Jul. 31, 2019USD ($)	May 31, 2019USD ($)	Jun. 30, 2019USD ($)mi	Jul. 01, 2019USD ($)	Feb. 28, 2019USD ($)	Jan. 31, 2019USD ($)	Apr. 30, 2018mi
MVP Joint Venture | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Ownership interest					45.50%
Maximum financial statement exposure					$ 2,004
MVP Southgate Project | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Ownership interest					47.20%
Capital contribution payable to MVP Joint Venture					$ 4
MVP Southgate Project | Variable Interest Entity, Not Primary Beneficiary | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Capital call payments			$ 0.9
MVP Southgate Project | Variable Interest Entity, Not Primary Beneficiary | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Capital call payments	$ 1.5	$ 1.6
MVP Project | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Capital contribution payable to MVP Joint Venture				$ 352.3
MVP Project | Variable Interest Entity, Not Primary Beneficiary | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Capital call payments			$ 93.4
MVP Project | Variable Interest Entity, Not Primary Beneficiary | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Capital call payments	$ 144.5	$ 114.3
MVP
Schedule of Equity Method Investments [Line Items]
Length of pipeline (in miles) | mi					300
MVP | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee, remaining capital obligation, percentage							33.00%	33.00%
Issuance of performance guarantee								$ 261
MVP Southgate Project | EQM
Schedule of Equity Method Investments [Line Items]
Length of pipeline (in miles) | mi									70
MVP Southgate Project | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee							$ 14
Beneficial Owner | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest					66.67%
Performance Guarantee | MVP | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted					$ 280
Performance Guarantee | MVP | Variable Interest Entity, Not Primary Beneficiary | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted						$ 249

Investment in Unconsolidated _4

Investment in Unconsolidated Entity - Schedule of Unaudited Condensed Financial Statements for the Investment in Unconsolidated Equity (Details) - MVP Joint Venture - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Condensed Consolidated Balance Sheets
Current assets	$ 836,397		$ 836,397		$ 687,657
Non-current assets	4,033,475		4,033,475		3,223,220
Total assets	4,869,872		4,869,872		3,910,877
Current liabilities	420,534		420,534		617,355
Non-current liabilities	2,166		2,166		0
Equity	4,447,172		4,447,172		3,293,522
Total liabilities and equity	4,869,872		4,869,872		$ 3,910,877
Condensed Statements of Consolidated Operations
Environmental remediation reserve	26	$ 0	(2,166)	$ 0
Other income	1,785	743	4,698	1,277
Net interest income	23,700	6,989	43,935	12,638
AFUDC - equity	55,298	16,307	102,514	29,489
Net income	$ 80,809	$ 24,039	$ 148,981	$ 43,404

Debt - $3 Billion Facility (Det

Debt - $3 Billion Facility (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Oct. 31, 2018USD ($)
Debt Instrument [Line Items]
Letters of credit outstanding	$ 1,372,500,000		$ 1,372,500,000		$ 625,000,000
$3 Billion Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding	1,100,000,000		1,100,000,000		625,000,000
Letters of credit outstanding	1,000,000		1,000,000		$ 1,000,000
$3 Billion Credit Facility | Line of credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 3,000,000,000		3,000,000,000
Additional borrowing capacity			$ 750,000,000
Consolidated leverage ratio for certain measurement periods (not more than)	5		5
Consolidated leverage ratio (not more than)	5.50		5.50
Maximum amount of outstanding short-term loans at any time during the period	$ 1,200,000,000	$ 338,000,000		$ 420,000,000
Average daily balance of short-term loans outstanding	$ 1,043,000,000	$ 122,000,000	$ 993,000,000	$ 211,000,000
Weighted average annual interest rate	3.80%	3.40%	3.90%	3.20%
$3 Billion Credit Facility | Same-day swing line advances
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 250,000,000
$3 Billion Credit Facility | Letter of credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000,000		$ 400,000,000
$1 Billion Credit Facility | Line of credit
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 1,000,000,000

Debt - Eureka Credit Facility (

Debt - Eureka Credit Facility (Details) - Eureka Midstream, LLC - Line of credit - Eureka Credit Facility	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Oct. 31, 2018USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 400,000,000
Additional borrowing capacity	$ 100,000,000
Available additional borrowings	$ 500,000,000	$ 500,000,000	$ 500,000,000
Consolidated leverage ratio	4.75	4.75	4.75
Maximum consolidated leverage ratio for certain measurement periods following certain acquisitions	5.25	5.25	5.25
Consolidated interest ratio	2.50	2.50	2.50
Borrowings outstanding	$ 293,000,000	$ 293,000,000	$ 293,000,000
Maximum amount of outstanding short-term loans at any time during the period		293,000,000
Average daily balance of short-term loans outstanding		$ 277,000,000
Weighted average annual interest rate			4.50%
Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate			1.00%
Eurodollar | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate			1.75%
Eurodollar | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate			3.00%
Federal Funds Effective Rate
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate			0.75%
Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate			2.00%

Debt - EQM Term Loan Facility (

Debt - EQM Term Loan Facility (Details) - Line of credit - $2.5 Billion EQM Term Loan Facility - USD ($)	Apr. 25, 2018	Jun. 25, 2018	Jun. 25, 2018
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 2,500,000,000
Maximum amount of outstanding short-term loans at any time during the period		$ 1,825,000,000
Line of credit expiration period	364 days
Write off of deferred issuance costs			$ 3,000,000
Average daily balance of short-term loans outstanding		$ 1,231,000,000
Weighted average annual interest rate		3.30%

Debt - RMP $850 Million Facilit

Debt - RMP $850 Million Facility (Details) - USD ($)		Jul. 23, 2018	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Repayment of borrowings outstanding	[1]			$ 572,000,000	$ 2,596,500,000
RMP $850 Million Facility | Line of credit
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 850,000,000
Maximum amount of outstanding short-term loans at any time during the period			$ 325,000,000		336,000,000
Average daily balance of short-term loans outstanding			$ 305,000,000		$ 306,000,000
Weighted average annual interest rate			3.90%		3.80%
Repayment of borrowings outstanding		$ 260,000,000
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of the Drop-Down Transaction and the EQM-RMP Merger because these transactions were between entities under common control.

Debt - EQM 4.125% and 4.00% Sen

Debt - EQM 4.125% and 4.00% Senior Notes (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2016	Sep. 30, 2014
Senior Notes | EQM 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Interest rate (as a percent)	4.125%	4.125%
Aggregate principal amount		$ 500,000,000
Senior Notes | EQM 4.00 Senior Notes Due 2024
Debt Instrument [Line Items]
Interest rate (as a percent)	4.00%		4.00%
Aggregate principal amount			$ 500,000,000
Line of credit | $3 Billion Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 3,000,000,000

Debt - 2018 Senior Notes (Detai

Debt - 2018 Senior Notes (Details) - USD ($)	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2019
Line of credit | RMP $850 Million Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 850,000,000
Senior Notes
Debt Instrument [Line Items]
Net proceeds from offering	$ 2,465,800,000
Discount	11,800,000
Debt issuance costs	$ 22,400,000
Senior Notes | EQM 4.75% Senior Notes Due 2023
Debt Instrument [Line Items]
Interest rate (as a percent)	4.75%
Aggregate principal amount	$ 1,100,000,000
Senior Notes | EQM 5.50% Senior Notes Due 2028
Debt Instrument [Line Items]
Interest rate (as a percent)	5.50%
Aggregate principal amount	$ 850,000,000
Senior Notes | EQM 6.50% Senior Notes Due 2048
Debt Instrument [Line Items]
Interest rate (as a percent)	6.50%
Aggregate principal amount	$ 550,000,000

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
EES | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value of preferred interest	$ 112	$ 115
Level 3 | EES | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Value of preferred interest	127	122
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of long-term debt	3,459	3,457
Fair Value, Measurements, Recurring | Level 2 | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of long-term debt	$ 3,612	$ 3,425

Net Income per Limited Partne_3

Net Income per Limited Partner Unit and Cash Distributions - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		Aug. 13, 2019	Jul. 24, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Distribution Made to Limited Partner [Line Items]
Cash distribution to the company's common and subordinated unitholders declared (in dollars per share)	[1],[2]			$ 1.160	$ 1.09	$ 2.305	$ 2.155
Subsequent Event | Common Units
Distribution Made to Limited Partner [Line Items]
Cash distribution to the company's common and subordinated unitholders declared (in dollars per share)			$ 1.160
Subsequent Event | Series A Preferred Units
Distribution Made to Limited Partner [Line Items]
Cash distribution to the company's common and subordinated unitholders declared (in dollars per share)			$ 0.9339
Limited Partner Interests | Subsequent Event | Common Units
Distribution Made to Limited Partner [Line Items]
Cash distribution declared to the limited partner		$ 136
Phantom Share Units (PSUs)
Distribution Made to Limited Partner [Line Items]
Weighted average phantom unit awards included in the calculation of basic weighted average limited partner units outstanding (in shares)				24,007	21,041	22,896	20,506
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	Represents the cash distributions declared related to the period presented. See Note 12 .

Net Income per Limited Partne_4

Net Income per Limited Partner Unit and Cash Distributions - Schedule of Net Income Per Limited Partner Unit (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended					6 Months Ended
		Jun. 30, 2019		Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to EQM		$ 152,438	[1]	$ 6,506	$ 233,832	[1]	$ 404,369	[1]	$ 494,182	[1]
Less: Series A Preferred Units interest in net income	[1]	(22,979)			0		(22,979)		0
Less: pre-acquisition net income allocated to EQT	[1]	0			(72,620)		0		(155,752)
Less: general partner interest in net income – general partner units	[1]	0			(1,700)		0		(4,791)
Less: general partner interest in net income – IDRs	[1]	0			(68,121)		0		(112,285)
Limited partner interest in net income	[1]	129,459			91,391		381,390		221,354
Net income allocable to units	[1]	$ 129,459			$ 91,391		$ 381,390		$ 221,354
Weighted average limited partner common units outstanding – basic (in shares)	[1]	200,482,000			83,553,000		177,498,000		82,290,000
Weighted average limited partner common units outstanding – diluted (in shares)	[1]	207,482,000			83,553,000		195,645,000		82,290,000
Net income per limited partner common unit – basic (in dollars per share)	[1],[2]	$ 0.65			$ 1.09		$ 2.15		$ 2.69
Net income per limited partner common unit – diluted (in dollars per share)	[1],[2]	$ 0.62			$ 1.09		$ 2.07		$ 2.69
Common Units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Limited partner interest in net income		$ 129,459			$ 91,391		$ 381,390		$ 221,354
Net income allocable to units		129,459			91,391		381,390		221,354
Class B Units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Limited partner interest in net income		0			0		0		0
Net income allocable to units		$ 0			$ 0		$ 0		$ 0
Units included in the calculation of diluted weighted average limited partner units outstanding (in shares)		7,000,000					7,000,000
Series A Preferred Units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Units included in the calculation of diluted weighted average limited partner units outstanding (in shares)							11,147,148
[1]	As discussed in Notes 1 and 2 , the consolidated financial statements of EQM have been retrospectively recast to include the pre-acquisition results of EQM Olympus Midstream LLC (EQM Olympus), Strike Force Midstream Holdings LLC (Strike Force) and EQM West Virginia Midstream LLC (EQM WV), which were acquired by EQM effective on May 1, 2018 (the Drop-Down Transaction), and Rice Midstream Partners LP (RMP), which was acquired by EQM effective on July 23, 2018 (the EQM-RMP Merger), because these transactions were between entities under common control.
[2]	See Note 12 for further disclosure on EQM's calculation of net income per limited partner unit (basic and diluted).