EQM Midstream Partners 10-K 15 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Entity Registrant Name	EQT Midstream Partners, LP
Entity Central Index Key	1,540,947
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 4.4
Common Units
Entity Common Stock, Shares Outstanding		80,581,758
General Partner Units
Entity Common Stock, Shares Outstanding		1,443,015

STATEMENTS OF CONSOLIDATED OPER

STATEMENTS OF CONSOLIDATED OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Operating revenues	[1],[2]	$ 834,096	$ 735,614	$ 632,936
Operating expenses:
Operating and maintenance	[1],[3]	84,717	73,213	70,103
Selling, general and administrative	[1],[3]	71,186	72,761	61,902
Depreciation and amortization	[1],[4]	97,485	62,691	49,895
Total operating expenses	[1]	253,388	208,665	181,900
Operating income	[1]	580,708	526,949	451,036
Other income	[1],[5]	27,377	37,918	8,694
Net interest expense	[1],[6]	36,181	16,766	21,345
Income before income taxes	[1]	571,904	548,101	438,385
Income tax expense (benefit)	[1]	0	10,147	(16,741)
Net income	[1],[4],[7]	571,904	537,954	455,126
Calculation of limited partners' interest in net income:
Net income	[1],[4],[7]	571,904	537,954	455,126
Less pre-acquisition income allocated to parent	[1]	0	(21,861)	(72,782)
Less general partner interest in net income - general partner units	[1]	(10,060)	(9,173)	(7,455)
Less general partner interest in net income - incentive distribution rights	[1]	(143,531)	(93,568)	(46,992)
Limited partners' interest in net income	[1]	$ 418,313	$ 413,352	$ 327,897
Net income per limited partner unit - basic (in USD per share)	[1]	$ 5.19	$ 5.21	$ 4.71
Net income per limited partner unit - diluted (in USD per share)	[1]	$ 5.19	$ 5.21	$ 4.70
Weighted average limited partner units outstanding – basic (in shares)	[1]	80,603	79,367	69,612
Weighted average limited partner units outstanding – diluted (in shares)	[1]	80,603	79,388	69,773
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	Operating revenues included affiliate revenues from EQT Corporation and subsidiaries (collectively, EQT) of $605.1 million, $551.4 million and $462.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.
[3]	Operating and maintenance expense included charges from EQT of $40.0 million, $34.2 million and $33.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Selling, general and administrative expense included charges from EQT of $67.4 million, $67.3 million and $55.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.
[4]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[5]	For the year ended December 31, 2017, other income included equity income from Mountain Valley Pipeline, LLC (MVP Joint Venture) of $22.2 million. For the year ended December 31, 2016, other income included distributions received from EQT Energy Supply, LLC (EES) of $8.3 million and equity income from the MVP Joint Venture of $9.9 million. For the year ended December 31, 2015, other income included equity income from the MVP Joint Venture of $2.4 million. See Note 6.
[6]	For the years ended December 31, 2017 and 2016, net interest expense included interest income on the preferred interest (the Preferred Interest) in EES of $6.8 million and $1.7 million, respectively.
[7]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

STATEMENTS OF CONSOLIDATED OPE3

STATEMENTS OF CONSOLIDATED OPERATIONS (Footnotes) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating and maintenance expense	[1],[2]	$ 84,717	$ 73,213	$ 70,103
Selling, general and administrative expense	[1],[2]	71,186	72,761	61,902
Equity income	[3]	22,171	9,898	2,367
EQT and Subsidiaries
Operating revenues from related party		605,100	551,400	462,400
Operating and maintenance expense		39,957	34,179	33,452
Selling, general and administrative expense		67,424	67,345	55,092
EES
Interest income		6,818	1,740	0
Variable Interest Entity, Not Primary Beneficiary | EES
Distributions included in other income			8,300
Other income | Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture
Equity income		$ 22,200	$ 9,900	$ 2,400
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	Operating and maintenance expense included charges from EQT of $40.0 million, $34.2 million and $33.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Selling, general and administrative expense included charges from EQT of $67.4 million, $67.3 million and $55.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.
[3]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

STATEMENTS OF CONSOLIDATED CASH

STATEMENTS OF CONSOLIDATED CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Cash flows from operating activities:
Net income	[1],[2],[3]	$ 571,904	$ 537,954		$ 455,126
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	[1],[3]	97,485	62,691		49,895
Deferred income taxes	[1]	0	8,774		(30,686)
Equity income	[1]	(22,171)	(9,898)		(2,367)
AFUDC – equity	[1]	(5,110)	(19,402)		(6,327)
Non-cash long term compensation expense	[1]	225	195		1,467
Changes in other assets and liabilities:
Accounts receivable	[1]	(8,142)	(2,872)		(647)
Accounts payable	[1]	4,821	(9,354)		8,470
Due to/from EQT affiliates	[1]	3,111	(34,667)		8,633
Other assets and other liabilities	[1]	8,427	4,483		6,142
Net cash provided by operating activities	[1]	650,550	537,904		489,706
Cash flows from investing activities:
Capital expenditures	[1]	(301,584)	(584,819)		(458,056)
Acquisitions - net assets from EQT (see Note 2)	[1]	0	(62,372)		(386,791)
MVP Interest Acquisition (see Note 2) and capital contributions to the MVP Joint Venture	[1]	(159,550)	(98,399)		(84,381)
Sales of interests in the MVP Joint Venture	[1]	0	12,533		9,723
Preferred Interest Acquisition (as defined in Note 2)	[1]	0	0		(124,317)
Principal payments received on the Preferred Interest (see Note 2)	[1]	4,166	1,024		0
Net cash used in investing activities	[1]	(456,968)	(732,033)		(1,043,822)
Cash flows from financing activities:
Proceeds from the issuance of EQM common units, net of offering costs	[1]	0	217,102		1,183,921
Acquisitions - purchase price in excess of net assets from EQT (see Note 2)	[1]	0	(3,734)		(486,392)
Acquisition of AVC net assets from EQT (see Note 2)	[1]	0	(208,894)		0
Proceeds from credit facility borrowings	[1]	524,000	740,000		617,000
Payments of credit facility borrowings	[1]	(344,000)	(1,039,000)		(318,000)
Proceeds from the issuance of long-term debt	[1]	0	500,000		0
Net contributions from (distributions to) EQT	[1]	0	20,234		(6,598)
Capital contributions	[1]	3,052	5,884		1,781
Distributions paid to unitholders	[1]	(432,188)	(329,471)		(212,262)
Discount, debt issuance costs and credit facility origination fees	[1]	(2,257)	(8,580)		0
Net cash (used in) provided by financing activities	[1]	(251,393)	(106,459)		779,450
Net change in cash and cash equivalents	[1]	(57,811)	(300,588)		225,334
Cash and cash equivalents at beginning of year	[1]	60,368	360,956		135,622
Cash and cash equivalents at end of year	[1]	2,557	60,368		360,956
Cash paid during the year for:
Interest, net of amount capitalized	[1]	41,958	13,899		19,606
Non-cash activity during the year:
Increase (decrease) in capital contribution receivable from EQT	[1]	12,411	(5,283)		5,744
Elimination of net current and deferred tax liabilities	[1]	0	93,951		84,446
Asset adjustments prior to acquisition	[1]	0	(115,270)	[2],[4]	0
Limited partner and general partner units issued for acquisitions	[1]	0	0		52,500
Net settlement of current income taxes receivable with EQT	[1]	$ 0	$ 0		$ 8,652
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[3]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[4]	Represents a decrease in the carrying value of the Gathering Assets and regulatory assets on the books of AVC, Rager, and the Gathering Assets by EQT prior to the October 2016 Acquisition.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	[1]	$ 2,557	$ 60,368
Accounts receivable (net of allowance for doubtful accounts of $446 and $319 as of December 31, 2017 and 2016, respectively)		28,804	20,662
Accounts receivable – affiliate		103,304	81,358
Other current assets		12,662	9,671
Total current assets		147,327	172,059
Property, plant and equipment		3,200,108	2,894,858
Less: accumulated depreciation		(396,049)	(316,024)
Net property, plant and equipment		2,804,059	2,578,834
Investment in unconsolidated entity		460,546	184,562
Other assets		136,895	140,385
Total assets		3,548,827	3,075,840
Current liabilities:
Accounts payable		47,040	35,830
Due to related party		31,673	19,027
Capital contribution payable to MVP Joint Venture		105,734	11,471
Accrued interest		10,926	12,016
Accrued liabilities		16,871	8,648
Total current liabilities		212,244	86,992
Credit facility borrowings		180,000	0
Senior notes		987,352	985,732
Regulatory and other long-term liabilities		20,273	9,562
Total liabilities		1,399,869	1,082,286
Equity:
Common (80,581,758 units issued and outstanding at December 31, 2017 and 2016)		2,147,706	2,008,510
General partner (1,443,015 units issued and outstanding at December 31, 2017 and 2016)		1,252	(14,956)
Total equity	[2]	2,148,958	1,993,554
Total liabilities and equity		$ 3,548,827	$ 3,075,840
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 446	$ 319
Common units issued (in shares)	80,581,758	80,581,758
Common units outstanding (in shares)	80,581,758	80,581,758
General partner interest, units issued (in shares)	1,443,015	1,443,015
General partner interest, units outstanding (in shares)	1,443,015	1,443,015

STATEMENTS OF CONSOLIDATED EQUI

STATEMENTS OF CONSOLIDATED EQUITY - USD ($) $ in Thousands		Total		Limited Partners Common	Limited Partners Subordinated	General Partner	Predecessor Equity
Beginning balance at Dec. 31, 2014	[1]	$ 1,211,326		$ 1,647,910	$ (929,374)	$ (27,497)	$ 520,287
Increase (Decrease) in Partners' Capital
Net income	[1]	455,126	[2],[3]	327,897		54,447	72,782
Capital contributions	[1]	7,492		7,342		150
Equity-based compensation plans	[1]	1,570		1,537		33
Net contributions (distributions) from EQT	[1]	(15,179)					(15,179)
Distributions to unitholders	[1]	(212,262)		(162,040)	(10,057)	(40,165)
Conversion of subordinated units to common units	[1],[4]	0		(939,431)	939,431
Proceeds from issuance of common units, net of offering costs	[1]	1,183,921		1,182,002		1,919
Elimination of net current and deferred tax liabilities	[1]	84,446					84,446
Asset adjustments prior to acquisition	[2]	0
Net assets from EQT	[1]	(386,791)					(386,791)
Issuance of units	[1]	52,500		38,910		13,590
Purchase price in excess of net assets from EQT	[1]	(538,892)		(505,452)		(33,440)
Ending balance at Dec. 31, 2015	[1]	1,843,257		1,598,675	$ 0	(30,963)	275,545
Increase (Decrease) in Partners' Capital
Net income	[1]	537,954	[2],[3]	413,352		102,741	21,861
Capital contributions	[1]	602		591		11
Equity-based compensation plans	[1]	195		195
Net contributions (distributions) from EQT	[1]	20,234					20,234
Elimination of capital lease	[1],[5]	0		23,500		1,555	(25,055)
Distributions to unitholders	[1]	(329,471)		(241,403)		(88,068)
Proceeds from issuance of common units, net of offering costs	[1]	217,102		217,102
Elimination of net current and deferred tax liabilities	[1]	93,951					93,951
Asset adjustments prior to acquisition	[1],[6]	(115,270)	[2]				(115,270)
Net assets from EQT	[1]	(271,266)					(271,266)
Purchase price in excess of net assets from EQT	[1]	(3,734)		(3,502)		(232)
Ending balance at Dec. 31, 2016	[1]	1,993,554		2,008,510		(14,956)	$ 0
Increase (Decrease) in Partners' Capital
Net income	[1]	571,904	[2],[3]	418,313		153,591
Capital contributions	[1]	15,463		15,184		279
Equity-based compensation plans	[1]	225		225
Distributions to unitholders	[1]	(432,188)		(294,526)		(137,662)
Asset adjustments prior to acquisition	[2]	0
Ending balance at Dec. 31, 2017	[1]	$ 2,148,958		$ 2,147,706		$ 1,252
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[3]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[4]	All subordinated units were converted to common units on a one-for-one basis on February 17, 2015. For purposes of calculating net income per common and subordinated unit, the conversion of the subordinated units was deemed to have occurred on January 1, 2015. See Note 3.
[5]	Reflects the elimination of the historical capital lease depreciation expense as described in Note 2.
[6]	Represents a decrease in the carrying value of the Gathering Assets and regulatory assets on the books of AVC, Rager, and the Gathering Assets by EQT prior to the October 2016 Acquisition.

Summary of Operations and Signi

Summary of Operations and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Operations and Significant Accounting Policies	Summary of Operations and Significant Accounting Policies Organization and Basis of Presentation EQT Midstream Partners, LP and subsidiaries (collectively, EQM) is a growth-oriented Delaware limited partnership formed by EQT in January 2012. EQT Midstream Services, LLC (EQM General Partner) is a direct wholly owned subsidiary of EQT GP Holdings, LP (EQGP) and is the general partner of EQM. References in these consolidated financial statements to EQT refer collectively to EQT Corporation and its consolidated subsidiaries. As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast for all periods presented to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM on October 13, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control. EQM does not have any employees. Operational, management and other services for EQM are provided by employees of EQT and its subsidiaries. Nature of Business EQM is a growth-oriented limited partnership formed by EQT to own, operate, acquire and develop midstream assets in the Appalachian Basin. EQM provides midstream services to EQT and third parties in Pennsylvania, West Virginia and Ohio through two primary assets: the gathering system and the transmission and storage system. As of December 31, 2017 , EQM's gathering system included approximately 300 miles of high pressure gathering lines with approximately 2.3 Bcf per day of total firm contracted gathering capacity and multiple interconnect points with EQM's transmission and storage system. EQM's gathering system also includes approximately 1,500 miles of Federal Energy Regulatory Commission (FERC)-regulated low pressure gathering lines. Revenues are primarily generated from EQM's firm gathering contracts. As of December 31, 2017 , EQM's transmission and storage system included an approximately 950 -mile FERC-regulated interstate pipeline that connects to seven interstate pipelines and to local distribution companies. The transmission system is supported by 18 associated natural gas storage reservoirs with approximately 645 MMcf per day of peak withdrawal capacity and 43 Bcf of working gas capacity and 41 compressor units. As of December 31, 2017 , the transmission assets had total throughput capacity of approximately 4.4 Bcf per day. Revenues are primarily generated from EQM's firm transmission and storage contracts. Significant Accounting Policies Principles of Consolidation : The consolidated financial statements include the accounts of all entities in which EQM holds a controlling financial interest. EQM applies the equity method of accounting where it can exert significant influence over, but does not control or direct the policies, decisions or activities of an entity. The consolidated financial statements reflect the pre-acquisition results of businesses acquired through common control transactions on a combined basis with EQM. See Note 2. Transactions between EQM and EQT have been identified in the consolidated financial statements as transactions between related parties and are discussed in Note 5. Segments: Operating segments are revenue-producing components of the enterprise for which separate financial information is produced internally and are subject to evaluation by EQM's chief operating decision maker in deciding how to allocate resources. EQM reports its operations in two segments, which reflect its lines of business. Gathering primarily includes high pressure gathering lines and the FERC-regulated low pressure gathering system. Transmission includes EQM's FERC-regulated interstate pipeline and storage business. The operating segments are evaluated on their contribution to EQM's operating income. All of EQM's operating revenues, income from continuing operations and assets are generated or located in the United States. See Note 4. Reclassification: Certain previously reported amounts have been reclassified to conform to the current year presentation. Use of Estimates: The preparation of financial statements in conformity with United States generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Cash and Cash Equivalents: EQM considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Interest earned on cash equivalents is included as a reduction to net interest expense in the accompanying statements of consolidated operations. Trade and Other Receivables: Trade and other receivables are stated at their historical carrying amount. Judgment is required to assess the ultimate realization of accounts receivable, including assessing the probability of collection and the creditworthiness of customers. Based upon management's assessments, allowances for doubtful accounts were $0.4 million and $0.3 million at December 31, 2017 and 2016 , respectively. EQM also has receivables due from EQT as discussed in Note 5. Fair Value of Financial Instruments: EQM has categorized its assets and liabilities disclosed at fair value into a three-level fair value hierarchy, based on the priority of the inputs to the valuation technique. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The carrying value 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; these are considered Level 1 fair values. The carrying value of EQM's credit facility borrowings approximates fair value as the interest rates are based on prevailing market rates; this is considered a Level 1 fair value. As EQM's senior notes are not actively traded, their fair value is a Level 2 fair value measurement estimated using a standard industry income approach model which utilizes a discount rate based on market rates for debt with similar remaining time to maturity and credit risk. See Note 9. The fair value of the Preferred Interest is a Level 3 fair value measurement which is estimated using an income approach model utilizing a market-based discount rate. As of December 31, 2017 and 2016 , the estimated fair value of the Preferred Interest was approximately $133 million and $132 million , respectively, and the carrying value of the Preferred Interest was approximately $119 million and $123 million , respectively, inclusive of approximately $4 million , for each period, in other current assets in the consolidated balance sheets. Property, Plant and Equipment: EQM's property, plant and equipment are stated at depreciated cost. Maintenance projects that do not increase the overall life of the related assets are expensed as incurred. Expenditures that extend the useful life of the underlying asset are capitalized. EQM capitalized internal costs of $46.5 million , $53.2 million and $78.9 million in 2017 , 2016 and 2015 , respectively. EQM capitalized interest of $4.1 million , $9.4 million and $5.6 million on assets under construction in 2017 , 2016 and 2015 , respectively, including the debt component of allowance for funds used during construction (AFUDC). As of December 31, 2017 2016 (Thousands) Gathering assets $ 1,526,028 $ 1,330,998 Accumulated depreciation (147,575 ) (110,473 ) Net gathering assets 1,378,453 1,220,525 Transmission and storage assets 1,674,080 1,563,860 Accumulated depreciation (248,474 ) (205,551 ) Net transmission and storage assets 1,425,606 1,358,309 Net property, plant and equipment $ 2,804,059 $ 2,578,834 Depreciation is recorded using composite rates on a straight-line basis over the estimated useful life of the assets. The overall rates of depreciation for the years ended December 31, 2017 , 2016 and 2015 were approximately 2.7% , 2.2% and 2.1% , respectively. EQM estimates pipelines have useful lives ranging from 20 years to 65 years and compression equipment has useful lives ranging from 20 years to 50 years . As circumstances warrant, depreciation estimates are reviewed to determine if any changes in the underlying assumptions are necessary. For EQM's regulated fixed assets, depreciation rates are re-evaluated each time it files with the FERC for a change in its transmission and storage rates. Whenever events or changes in circumstances indicate that the carrying amount of long-lived assets may not be recoverable, EQM reviews its long-lived assets for impairment by first comparing the carrying value of the assets to the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the assets. If the carrying value exceeds the sum of the assets' undiscounted cash flows, EQM estimates an impairment loss equal to the difference between the carrying value and fair value of the assets. Investment in Unconsolidated Entity: EQM evaluates its investment in unconsolidated entity for impairment whenever events or changes in circumstances indicate that the carrying value of the investment may have experienced a decline in value. When there is evidence of loss in value that is other than temporary, EQM compares the estimated fair value of the investment to the carrying value of the investment to determine whether impairment has occurred. If the estimated fair value is less than the carrying value, the excess of the carrying value over the estimated fair value is recognized as an impairment loss. Unamortized Debt Discount and Issuance Expense: Discounts and expenses incurred with the issuance of EQM's senior notes are amortized over the term of the debt. These amounts are presented as a reduction of the debt on the accompanying consolidated balance sheets. Expenses incurred with the issuance and extension of EQM's $1 billion credit facility are presented in other assets on the accompanying consolidated balance sheets. Natural Gas Imbalances: EQM experiences natural gas imbalances when the actual amount of natural gas delivered from a pipeline system or storage facility differs from the amount of natural gas scheduled to be delivered. EQM values these imbalances due to or from shippers and operators at current index prices. Imbalances are settled in-kind, subject to the terms of the FERC tariffs. Imbalances as of December 31, 2017 and 2016 were receivables of $5.2 million and $2.8 million , respectively, included in other current assets in the accompanying consolidated balance sheets with offsetting amounts recorded to system gas, a component of property, plant and equipment. EQM classifies imbalances as current as it expects to settle them within a year. Asset Retirement Obligations: EQM is under no legal or contractual obligation to restore or dismantle its gathering system and transmission and storage system upon abandonment. Additionally, EQM operates and maintains its gathering system and transmission and storage system and it intends to do so as long as supply and demand for natural gas exists, which EQM expects for the foreseeable future. Therefore, EQM does not have any asset retirement obligations as of December 31, 2017 and 2016 . Contingencies: EQM is involved in various regulatory and legal proceedings that arise in the ordinary course of business. A liability is recorded for contingencies based upon EQM's assessment that a loss is probable and that the amount of the loss can be reasonably estimated. EQM considers many factors in making these assessments, including history and specifics of each matter. Estimates are developed in consultation with legal counsel and are based upon the analysis of potential results. See Note 13. Regulatory Accounting: EQM's regulated operations consist of interstate pipeline, intrastate gathering and storage operations subject to regulation by the FERC. Rate regulation provided by the FERC is designed to enable EQM to recover the costs of providing the regulated services plus an allowed return on invested capital. The application of regulatory accounting allows EQM to defer expenses and income in its consolidated balance sheets as regulatory assets and liabilities when it is probable that those expenses and income will be allowed in the rate setting process in a period different from the period in which they would have been reflected in the statements of consolidated operations for a non-regulated entity. The deferred regulatory assets and liabilities are then recognized in the statements of consolidated operations in the period in which the same amounts are reflected in rates. The amounts deferred in the consolidated balance sheets relate primarily to the accounting for income taxes and post-retirement benefit costs. EQM believes that it will continue to be subject to rate regulation that will provide for the recovery of deferred costs. See Note 10. The following tables present the total regulated operating revenues and expenses, and the regulated property, plant and equipment of EQM. Years Ended December 31, 2017 2016 2015 (Thousands) Operating revenues $ 390,883 $ 347,320 $ 309,984 Operating expenses $ 151,510 $ 118,611 $ 109,954 As of December 31, 2017 2016 (Thousands) Property, plant & equipment $ 1,787,656 $ 1,675,433 Accumulated depreciation and amortization (278,756 ) (234,336 ) Net property, plant & equipment $ 1,508,900 $ 1,441,097 Revenue Recognition: Reservation revenues on firm contracted capacity are recognized ratably over the contract period based on the contracted volume regardless of the amount of natural gas transported or gathered. Revenues associated with gathered or transported volumes under firm and interruptible contracts are recognized as physical deliveries of natural gas are made. AFUDC: The carrying costs for the construction of certain long-lived regulated assets are capitalized and amortized over the related assets' estimated useful lives. The capitalized amount for construction of regulated assets includes interest cost (the debt component) and a designated cost of equity (the equity component) for financing the construction of these regulated assets. The debt components of AFUDC for the years ended December 31, 2017 , 2016 and 2015 of $0.8 million , $2.4 million and $1.6 million , respectively, were included as a reduction of net interest expense in the statements of consolidated operations. The equity components of AFUDC for the years ended December 31, 2017 , 2016 and 2015 of $5.1 million , $19.4 million and $6.3 million , respectively, were recorded in other income in the statements of consolidated operations. Equity-Based Compensation: EQM has awarded equity-based compensation in connection with the EQT Midstream Services, LLC 2012 Long-Term Incentive Plan. These awards will be paid in EQM common units; therefore, EQM treats these programs as equity awards. Awards are recorded at fair value which utilizes the published market price on the grant date. See Note 8. 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. EQM's net income is allocated to the general partner and limited partners in accordance with their respective ownership percentages, and when applicable, giving effect to incentive distributions allocable to the general partner. The allocation of undistributed earnings, or net income in excess of distributions, to the incentive distribution rights (IDRs) is limited to available cash (as defined by EQM's partnership agreement) for the period. Any common units issued during the period are included on a monthly weighted-average basis for the periods in which they were outstanding. Diluted net income per limited partner unit reflects the potential dilution that could occur if securities or agreements to issue common units, such as awards under the long-term incentive plan, were exercised, settled or converted into EQM common units. When it is determined that potential common units resulting from an award subject to performance or market conditions should be included in the diluted net income per limited partner unit calculation, the impact is reflected by applying the treasury stock method. Net income attributable to AVC, Rager and the Gathering Assets for the periods prior to October 1, 2016 and to NWV Gathering for the periods prior to March 17, 2015 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 unitholders. The phantom units granted to the independent directors of the EQM General Partner will be paid in common units upon a director's termination of service on the EQM General Partner's Board of Directors. As there are no remaining service, performance or market conditions related to these awards, 20,959 , 17,196 and 14,017 phantom unit awards were included in the calculation of basic and diluted weighted average limited partner units outstanding for the years ended December 31, 2017 , 2016 and 2015 , respectively. Potentially dilutive securities included in the calculation of diluted weighted average limited partner units outstanding totaled zero , 20,548 and 160,633 for the years ended December 31, 2017 , 2016 and 2015 , respectively. Income Taxes: For federal and state income tax purposes, all income, expenses, gains, losses and tax credits generated flow through to EQM's unitholders; accordingly, there is no provision for income taxes for EQM. Net income for financial statement purposes may differ significantly from taxable income of unitholders because of differences between the tax basis and financial reporting basis of assets and liabilities and the taxable income allocation requirements under EQM's partnership agreement. The aggregate difference in the basis of EQM's net assets for financial and tax reporting purposes cannot be readily determined because information regarding each partner's tax attributes is not available to EQM. See Note 11. Recently Issued Accounting Standards: In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers . The standard requires an entity to recognize revenue in a manner that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date which approved a one year deferral of ASU 2014-09 to annual reporting periods beginning after December 15, 2017. During the third quarter of 2017, EQM substantially completed its detailed review of the impact of the standard on each of its contracts. EQM adopted the ASUs using the modified retrospective method of adoption on January 1, 2018 and EQM did not require an adjustment to the opening balance of equity. EQM does not expect the standard to have a significant impact on its results of operations, liquidity or financial position in 2018. Additional disclosures will be required to describe the nature, amount, timing and uncertainty of revenue and cash flows from contracts with customers including disaggregation of revenue and remaining performance obligations. EQM implemented processes and controls to ensure new contracts are reviewed for the appropriate accounting treatment and to generate the disclosures required under the new standard in the first quarter of 2018. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities . The changes primarily affect the accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. This standard will eliminate the cost method of accounting for equity investments. The ASU will be effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period, with early adoption of certain provisions permitted. EQM will adopt this standard in the first quarter of 2018 and does not expect that the adoption will have a material impact on its financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases . The primary effect of adopting the new standard on leases will be to record assets and obligations for contracts currently recognized as operating leases. Lessees and lessors must apply a modified retrospective transition approach. The ASU will be effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early adoption permitted. EQM has completed a high level identification of agreements covered by this standard and will continue to evaluate the impact this standard will have on its financial statements, internal controls and related disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments. This ASU 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 ASU eliminates the probable initial recognition threshold in current GAAP and, instead, requires an entity to reflect 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 that have the contractual right to receive cash. The ASU will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. EQM is currently evaluating the impact this standard will have on its financial statements and related disclosures. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments . This ASU addresses the presentation and classification of eight specific cash flow issues. The amendments in the ASU will be effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period, with early adoption permitted. EQM adopted this standard in the second quarter of 2017 with no material impact on its financial statements and related disclosures. Subsequent Events: EQM has evaluated subsequent events through the date of the financial statement issuance.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	Acquisitions The following table presents EQM's acquisitions completed during the three years ended December 31, 2017 . Acquisition Date Total Consideration Cash Common Units Issued to EQT GP Units Issued to EQT (Thousands, except unit amounts) NWV Gathering Acquisition (a) 3/17/15 $ 925,683 $ 873,183 511,973 178,816 MVP Interest Acquisition (b) 3/30/15 54,229 54,229 — — Preferred Interest Acquisition (c) 4/15/15 124,317 124,317 — — October 2016 Acquisition (d) 10/13/16 $ 275,000 $ 275,000 — — (a) EQT contributed NWV Gathering to EQM Gathering Opco, LLC (EQM Gathering), an indirect wholly owned subsidiary of EQM. The cash portion of the purchase price was funded with net proceeds from an equity offering of EQM common units and borrowings under EQM's credit facility. (b) EQM assumed 100% of the membership interests in MVP Holdco, LLC (MVP Holdco), the owner of the interest (the MVP Interest) in the MVP Joint Venture, which at the time was an indirect wholly owned subsidiary of EQT. The cash payment made represented EQM's reimbursement to EQT for 100% of the capital contributions made by EQT to the MVP Joint Venture as of March 30, 2015. The cash payment was funded by borrowings under EQM's credit facility. See Note 6. (c) Pursuant to the NWV Gathering Acquisition contribution and sale agreement, EQM acquired the Preferred Interest from EQT in EES, which at the time was an indirect wholly owned subsidiary of EQT. EES generates revenue from services provided to a local distribution company. The cash payment was funded by borrowings under EQM's credit facility. In October 2016, the operating agreement of EES was amended to include mandatory redemption of the Preferred Interest at the end of the preference period, which is expected to be December 31, 2034. As a result of this amendment, the accounting for EQM's investment in EES converted from a cost method investment to a note receivable effective October 1, 2016. This conversion did not impact the carrying value of this instrument; however, distributions from EES subsequent to the amendment were recorded partly as a reduction in the Preferred Interest and partly as interest income, which is included in net interest expense in the accompanying statements of consolidated operations. Distributions received from EES prior to this amendment were included in other income in the accompanying statements of consolidated operations. (d) On October 13, 2016, EQM entered into a Purchase and Sale Agreement with EQT pursuant to which EQM acquired from EQT 100% of the outstanding limited liability company interests of AVC and Rager as well as the Gathering Assets. The closing occurred on October 13, 2016 and was effective as of October 1, 2016. The cash payment was funded by borrowings under EQM's credit facility. AVC, Rager, the Gathering Assets and NWV Gathering 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 October 2016 Acquisition and NWV Gathering Acquisition as if the entities were owned for all periods presented; however, the consolidated financial statements are not necessarily indicative of the results of operations that would have occurred if EQM had owned them during the periods reported. Prior to the October 2016 Acquisition, EQM operated the AVC facilities as part of its transmission and storage system under a lease agreement with EQT. The lease was a capital lease under GAAP; therefore, revenues and expenses associated with the AVC facilities were included in EQM's historical consolidated financial statements and the AVC facilities were depreciated over the lease term of 25 years. In conjunction with the October 2016 Acquisition, the lease agreement was terminated. As a result, EQM's recast of the consolidated financial statements included recasting depreciation expense recognized for the periods prior to the transaction to reflect the pipeline's useful life of 40 years . The $25.1 million of cumulative capital lease depreciation recorded for periods prior to the transaction was eliminated through equity at the time of the acquisition and the financial statements now reflect the depreciation expense based on the 40 year useful life. This adjustment increased previously reported net income by $5.2 million and $4.2 million for the years ended December 31, 2016 and 2015, respectively. In addition, because the effect of the recast of the financial statements resulted in the elimination of the capital lease obligation from EQM to AVC, the lease obligation portion of the consideration paid was recorded in financing activities in the statements of consolidated cash flows.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity	Equity The following table summarizes EQM's public offerings of its common units during the three years ended December 31, 2017 . Common Units Issued GP Units Issued Price Per Unit Net Proceeds Underwriters' Discount and Other Offering Expenses (Thousands, except unit and per unit amounts) March 2015 equity offering (a) 9,487,500 25,255 $ 76.00 $ 696,582 $ 24,468 $750 Million At the Market (ATM) Program in 2015 (b) 1,162,475 — 74.92 85,483 1,610 November 2015 equity offering (c) 5,650,000 — 71.80 399,937 5,733 $750 Million ATM Program in 2016 (d) 2,949,309 — $ 74.42 $ 217,102 $ 2,381 (a) The underwriters exercised their option to purchase additional common units. The EQM General Partner purchased 25,255 EQM general partner units for approximately $1.9 million to maintain its then 2.0% general partner ownership percentage. This amount was included in net proceeds from this offering. The net proceeds were used to finance a portion of the cash consideration paid to EQT in connection with the NWV Gathering Acquisition as described in Note 2. (b) During the third quarter of 2015, EQM entered into an equity distribution agreement that established an ATM common unit offering program, pursuant to which a group of managers, acting as EQM's sales agents, may sell EQM common units having an aggregate offering price of up to $750 million (the $750 Million ATM Program). The price per unit represents an average price for all issuances under the $750 Million ATM Program in 2015. The underwriters' discount and other offering expenses in the table above include commissions of approximately $0.9 million . EQM used the net proceeds for general partnership purposes. Prior to this $750 Million ATM Program, the EQM General Partner maintained its general partner ownership percentage at the previous level of 2.0% . Starting with sales under the $750 Million ATM Program in 2015, the EQM General Partner elected not to maintain its general partner ownership percentage. (c) The net proceeds were used for general partnership purposes and to repay amounts outstanding under EQM's credit facility. (d) The price per unit represents an average price for all issuances under the $750 Million ATM Program in 2016. The underwriters' discount and other offering expenses in the table above include commissions of approximately $2.2 million . EQM used the net proceeds for general partnership purposes. The following table summarizes EQM's common, subordinated and general partner units issued and outstanding during the three years ended December 31, 2017 . There were no issuances in 2017. Limited Partner Units General Common Subordinated Partner Units Total Balance at January 1, 2015 43,347,452 17,339,718 1,238,514 61,925,684 Conversion of subordinated units to common units 17,339,718 (17,339,718 ) — — 2014 EQM VDA issuance 21,063 — 430 21,493 March 2015 equity offering 9,487,500 — 25,255 9,512,755 NWV Gathering Acquisition consideration 511,973 — 178,816 690,789 $750 Million ATM Program 1,162,475 — — 1,162,475 November 2015 equity offering 5,650,000 — — 5,650,000 Balance at December 31, 2015 77,520,181 — 1,443,015 78,963,196 2014 EQM VDA issuance 19,796 — — 19,796 EQM Total Return Program issuance 92,472 — — 92,472 $750 Million ATM Program 2,949,309 — — 2,949,309 Balance at December 31, 2016 and 2017 80,581,758 — 1,443,015 82,024,773 Upon payment of the cash distribution for the fourth quarter of 2014, the financial requirements for the conversion of all subordinated units were satisfied. As a result, on February 17, 2015, the 17,339,718 subordinated units converted into common units on a one -for-one basis. For purposes of calculating net income per common and subordinated unit, the conversion of the subordinated units was deemed to have occurred on January 1, 2015. EQM issued 19,796 and 21,063 common units under the 2014 EQM Value Driver Award Program (2014 EQM VDA) in February 2016 and 2015, respectively, as discussed in Note 8. In connection with the February 2015 issuance, the EQM General Partner purchased 430 EQM general partner units to maintain its then 2.0% general partner ownership percentage. EQM issued 92,472 common units under the EQM Total Return Program in February 2016 as discussed in Note 8. As of December 31, 2017 , EQGP and its subsidiaries owned 21,811,643 EQM common units, representing a 26.6% limited partner interest, 1,443,015 EQM general partner units, representing a 1.8% general partner interest, and all of the IDRs in EQM. As of December 31, 2017 , EQT owned 100% of the non-economic general partner interest and a 90.1% limited partner interest in EQGP.

Financial Information by Busine

Financial Information by Business Segment	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Financial Information by Business Segment	Financial Information by Business Segment Years Ended December 31, 2017 2016 2015 (Thousands) Revenues from external customers (including affiliates): Gathering $ 454,536 $ 397,494 $ 335,105 Transmission 379,560 338,120 297,831 Total operating revenues $ 834,096 $ 735,614 $ 632,936 Operating income: Gathering $ 333,563 $ 289,027 $ 243,257 Transmission 247,145 237,922 207,779 Total operating income $ 580,708 $ 526,949 $ 451,036 Reconciliation of operating income to net income: Other income 27,377 37,918 8,694 Net interest expense 36,181 16,766 21,345 Income tax expense (benefit) — 10,147 (16,741 ) Net income $ 571,904 $ 537,954 $ 455,126 As of December 31, 2017 2016 2015 (Thousands) Segment assets: Gathering $ 1,463,247 $ 1,292,713 $ 1,079,644 Transmission 1,487,501 1,413,631 1,183,641 Total operating segments 2,950,748 2,706,344 2,263,285 Headquarters, including cash 598,079 369,496 570,073 Total assets $ 3,548,827 $ 3,075,840 $ 2,833,358 Years Ended December 31, 2017 2016 2015 (Thousands) Depreciation and amortization: Gathering $ 38,796 $ 30,422 $ 24,360 Transmission 58,689 32,269 25,535 Total $ 97,485 $ 62,691 $ 49,895 Expenditures for segment assets: Gathering $ 196,871 $ 295,315 $ 225,537 Transmission 111,102 292,049 203,706 Total (a) $ 307,973 $ 587,364 $ 429,243 (a) 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 on the statements of consolidated cash flows until they are paid in a subsequent period. Accrued capital expenditures were approximately $33.1 million , $26.7 million , $24.1 million and $53.0 million at December 31, 2017 , 2016 , 2015 and 2014 , respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Affiliate Transactions . In the ordinary course of business, EQM engages in transactions with EQT and its affiliates including, but not limited to, gas gathering agreements, transportation service and precedent agreements and storage agreements. Omnibus Agreement . EQM entered into an omnibus agreement by and among EQM, the EQM General Partner and EQT. Pursuant to the omnibus agreement, EQT agreed to provide EQM with a license to use the name "EQT" and related marks in connection with EQM's business. EQM is allocated the portion of operating and maintenance expense and selling, general and administrative expense incurred by EQT for the benefit of EQM. The omnibus agreement also provides for certain indemnification and reimbursement obligations between EQT and EQM. Operation and Management Services Agreement . EQM had an operation and management services agreement with EQT Gathering, LLC (EQT Gathering), an indirect wholly owned subsidiary of EQT, pursuant to which EQT Gathering provided EQM's pipelines and storage facilities with certain operational and management services. EQM reimbursed EQT Gathering for such services pursuant to the terms of its omnibus agreement with EQT. The operation and management services agreement was replaced in its entirety by a secondment agreement with EQT (the Secondment Agreement). Secondment Agreement . On December 7, 2017, EQT, EQT Gathering, Equitrans, L.P. (Equitrans), EQM and the EQM General Partner entered into the Secondment Agreement, pursuant to which available employees of EQT and its affiliates may be seconded to EQM and its subsidiaries to provide operating and other services with respect to EQM's business under the direction, supervision and control of EQM or its subsidiaries. EQM reimburses EQT and its affiliates for the services provided by the seconded employees pursuant to the Secondment Agreement. The following table summarizes the amounts and categories of expenses for which EQM was obligated to reimburse EQT pursuant to the omnibus agreement and the Secondment Agreement, as applicable, and the amounts and categories of obligations for which EQT was obligated to indemnify and/or reimburse EQM pursuant to the omnibus agreement for the years ended December 31, 2017 , 2016 and 2015 . Years Ended December 31, 2017 2016 2015 (Thousands) Reimbursements to EQT Operating and maintenance expense (a) $ 39,957 $ 33,526 $ 31,310 Selling, general and administrative expense (a) $ 67,424 $ 63,255 $ 46,149 Reimbursements from EQT (b) Plugging and abandonment $ 4 $ 195 $ 26 Bare steel replacement 15,704 — 6,268 Other capital reimbursements $ — $ 162 $ 1,198 (a) The expenses for which EQM reimburses EQT and its subsidiaries may not necessarily reflect the actual expenses that EQM would incur on a stand-alone basis, and EQM is unable to estimate what those expenses would be on a stand-alone basis. These amounts exclude the recast impact of the October 2016 Acquisition and NWV Gathering Acquisition as these amounts do not represent reimbursements pursuant to the omnibus agreement. (b) These reimbursements were recorded as capital contributions from EQT. Summary of Related Party Transactions . The following table summarizes related party transactions for the years ended December 31, 2017 , 2016 and 2015 . Years Ended December 31, 2017 2016 2015 (Thousands) Operating revenues $ 605,099 $ 551,353 $ 462,371 Operating and maintenance expense (a) 39,957 34,179 33,452 Selling, general and administrative expense (a) 67,424 67,345 55,092 Other income (b) 22,171 18,191 2,367 Interest income on Preferred Interest (see Note 2) 6,818 1,740 — Principal payments received on Preferred Interest (see Note 2) 4,166 1,024 — Distributions to EQM General Partner (c) 235,167 169,438 109,194 Capital contributions from EQT 15,463 602 7,492 Net contributions from/(distributions to) EQT $ — $ 20,234 $ (15,179 ) (a) The expenses for which EQM reimburses EQT and its subsidiaries may not necessarily reflect the actual expenses that EQM would incur on a stand-alone basis, and EQM is unable to estimate what those expenses would be on a stand-alone basis. These amounts include the recast impact of the October 2016 Acquisition and NWV Gathering Acquisition as they represent the total amounts allocated to EQM by EQT for the periods presented. (b) For the year ended December 31, 2017 , other income included equity income from the MVP Joint Venture of $22.2 million . For the year ended December 31, 2016 , other income included distributions received from EES of $8.3 million and equity income from the MVP Joint Venture of $9.9 million . For the year ended December 31, 2015 , other income included equity income from the MVP Joint Venture of $2.4 million . See Note 6. (c) The distributions to the EQM General Partner are based on the period to which the distributions relate and not the period in which the distributions were declared and paid. For example, for the year ended December 31, 2017 , total distributions to the EQM General Partner included the cash distribution declared on January 18, 2018 related to the fourth quarter 2017 of $1.025 per common unit and the amounts related to its general partner interest and IDRs. The following table summarizes related party balances as of December 31, 2017 and 2016 . As of December 31, 2017 2016 (Thousands) Accounts receivable – affiliate $ 103,304 $ 81,358 Due to related party 31,673 19,027 Investment in unconsolidated entity 460,546 184,562 Preferred Interest in EES (see Note 1) $ 119,127 $ 123,293 See also Note 2, Note 3, Note 6, Note 7, Note 8, Note 9, Note 12 and Note 14 for further discussion of related party transactions.

Investment in Unconsolidated En

Investment in Unconsolidated Entity	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Entity	Investment in Unconsolidated Entity On March 30, 2015, EQM assumed EQT's interest in MVP Holdco, which owns the interest in the MVP Joint Venture, for $54.2 million . The MVP Joint Venture plans to construct the Mountain Valley Pipeline (MVP), an estimated 300 -mile natural gas interstate pipeline spanning from northern West Virginia to southern Virginia. EQM also assumed the role of operator of the MVP from EQT. In April 2015, October 2015 and January 2016, EQM sold 10% , 1% and 8.5% ownership interests in the MVP Joint Venture, respectively. The purchase from EQT and subsequent sales of interests in the MVP Joint Venture were all for consideration that represented the proportional amount of capital contributions made to the joint venture as of the date of the respective transactions. As of December 31, 2017 , EQM owned a 45.5% interest in the MVP Joint Venture. The MVP Joint Venture has been determined to be 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 because it does not have the power to direct the activities of the MVP Joint Venture that most significantly impact its economic performance. Certain business decisions, including, but not limited to, decisions about operating and construction budgets, project construction schedule, material contracts or precedent agreements, indebtedness, significant acquisitions or dispositions, material regulatory filings and strategic decisions require the approval of owners holding more than a 66 2/3% interest in the MVP Joint Venture and no one member owns more than a 66 2/3% interest. Beginning on the date it was assumed from EQT, EQM accounted for the MVP Interest as an equity method investment as EQM has the ability to exercise significant influence over operating and financial policies of the MVP Joint Venture. EQM records adjustments to the investment balance for contributions to or distributions from the MVP Joint Venture and its pro-rata share of earnings of the MVP Joint Venture. In December 2017 , the MVP Joint Venture issued a capital call notice to MVP Holdco for $105.7 million , of which $27.2 million was paid in January 2018 and the remaining $78.5 million is expected to be paid in February 2018 . The capital contribution payable has been reflected on the consolidated balance sheet as of December 31, 2017 with a corresponding increase to EQM's investment in the MVP Joint Venture. Equity income related to EQM's portion of the MVP Joint Venture's AFUDC on construction of the MVP is reported in other income in the statements of consolidated operations and was $22.2 million , $9.9 million and $2.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. As of December 31, 2017 , EQM had issued a $91 million performance guarantee in favor of the MVP Joint Venture to provide performance assurances for MVP Holdco's obligations to fund its proportionate share of the construction budget for the MVP. As of December 31, 2017 , EQM's maximum financial statement exposure related to the MVP Joint Venture was approximately $552 million , which consists of the investment in unconsolidated entity balance on the consolidated balance sheet as of December 31, 2017 and amounts which could have become due under EQM's performance guarantee as of that date. The following tables summarize the audited financial statements for the investment in unconsolidated entity accounted for under the equity method of accounting. Consolidated Balance Sheets As of December 31, 2017 2016 (Thousands) Current assets $ 330,271 $ 53,959 Noncurrent assets 747,728 361,820 Total assets $ 1,077,999 $ 415,779 Current liabilities $ 65,811 $ 10,149 Equity 1,012,188 405,630 Total liabilities and equity $ 1,077,999 $ 415,779 Statements of Consolidated Operations Years Ended December 31, 2017 2016 2015 (Thousands) AFUDC - equity $ 32,054 $ 16,315 $ 3,576 Net interest income 16,674 5,206 1,143 Net income $ 48,728 $ 21,521 $ 4,719

Cash Distributions

Cash Distributions	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Cash Distributions	Cash Distributions The EQM partnership agreement requires EQM to distribute all of its available cash to EQM unitholders within 45 days after the end of each quarter. Available cash generally means, for any quarter, all cash and cash equivalents on hand at the end of that quarter: • less , the amount of cash reserves established by the EQM General Partner to: • provide for the proper conduct of EQM's business (including reserves for future capital expenditures, anticipated future debt service requirements and refunds of collected rates reasonably likely to be refunded as a result of a settlement or hearing related to FERC rate proceedings or rate proceedings under applicable law subsequent to that quarter); • comply with applicable law, any of EQM's debt instruments or other agreements; or • provide funds for distributions to EQM's unitholders and to the EQM General Partner for any one or more of the next four quarters (provided that the EQM General Partner may not establish cash reserves for distributions if the effect of the establishment of such reserves will prevent EQM from distributing the minimum quarterly distribution on all common units); • plus , if the EQM General Partner so determines, all or any portion of the cash on hand on the date of determination of available cash for the quarter resulting from working capital borrowings made subsequent to the end of such quarter. All IDRs are held by the EQM General Partner. IDRs represent the right to receive an increasing percentage ( 13.0% , 23.0% and 48.0% ) of quarterly distributions of available cash from operating surplus after the minimum quarterly distribution and the target distribution levels described below have been achieved. The EQM General Partner may transfer the IDRs separately from its general partner interest, subject to restrictions in EQM's partnership agreement. The following discussion assumes that the EQM General Partner continues to own both its 1.8% general partner interest and the IDRs. If for any quarter EQM has distributed available cash from operating surplus to the common unitholders in an amount equal to EQM's minimum quarterly distribution; then, EQM will distribute any additional available cash from operating surplus for that quarter among the unitholders and the EQM General Partner in the following manner: Total Quarterly Marginal Percentage Interest in Distributions Unit Target Amount Unitholders General Partner Minimum Quarterly Distribution $0.35 98.2% 1.8% First Target Distribution Above $0.3500 up to $0.4025 98.2% 1.8% Second Target Distribution Above $0.4025 up to $0.4375 85.2% 14.8% Third Target Distribution Above $0.4375 up to $0.5250 75.2% 24.8% Thereafter Above $0.5250 50.2% 49.8% To the extent these incentive distributions are made to the EQM General Partner, more available cash proportionally is allocated to the EQM General Partner than to holders of limited partner units. On January 18, 2018 , the Board of Directors of the EQM General Partner declared a cash distribution to EQM's unitholders for the fourth quarter of 2017 of $1.025 per common unit. The cash distribution was paid on February 14, 2018 to unitholders of record at the close of business on February 2, 2018 . Cash distributions to EQGP were approximately $22.4 million related to its limited partner interest, $2.2 million related to its general partner interest and $41.1 million related to its IDRs.

Equity-Based Compensation Plan

Equity-Based Compensation Plan	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation Plan	Equity-Based Compensation Plan The EQM General Partner has granted equity-based phantom units that vested upon grant to the independent directors of the EQM General Partner. The value of the phantom units will be paid in EQM common units upon the director's termination of service on the EQM General Partner's Board of Directors. EQM accounted for these awards as equity awards and recorded compensation expense for the fair value of the awards at the grant date fair value. A total of 21,739 independent director unit-based awards, including accrued distributions, were outstanding as of December 31, 2017 . A total of 2,940 , 2,610 and 2,220 unit-based awards were granted to the independent directors during the years ended December 31, 2017 , 2016 and 2015 , respectively. The weighted average fair value of these grants, based on EQM's common unit price on the grant date, was $76.68 , $75.46 and $88.00 for the years ended December 31, 2017 , 2016 and 2015 , respectively. EQM recognized equity-based compensation expense of $0.2 million each year during the years ended December 31, 2017 , 2016 and 2015 related to these grants. In July 2012, the EQM General Partner granted awards representing common units (EQM Total Return Program). The confirmed awards were distributed in EQM common units during the first quarter of 2016. During the year ended December 31, 2015, EQM recognized equity-based compensation expense of $0.7 million related to these awards. In the first quarter of 2014, performance units under the 2014 EQM Value Driver Award Program (2014 EQM VDA) were granted to EQT employees who provided services to EQM. The first tranche of the confirmed awards were distributed in EQM common units in February 2015 and the remainder of the confirmed awards were distributed in EQM common units in February 2016. During the year ended December 31, 2015, EQM recognized equity-based compensation expense of $0.6 million related to these awards. EQM common units to be delivered pursuant to vesting of the equity-based awards may be common units acquired by the EQM General Partner in the open market or from any other person, issued directly by EQM or any combination of the foregoing.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt The following table presents EQM's outstanding debt as of December 31, 2017 and 2016 . December 31, 2017 December 31, 2016 Principal Carrying Value (a) Fair (b) Principal Carrying Value (a) Fair (b) (Thousands) $1 Billion Facility $ 180,000 $ 180,000 $ 180,000 $ — $ — $ — 364-Day Facility — — — — — — 4.00% Senior Notes due 2024 500,000 494,939 504,110 500,000 494,170 493,125 4.125% Senior Notes due 2026 500,000 492,413 501,990 500,000 491,562 488,460 Total debt $ 1,180,000 $ 1,167,352 $ 1,186,100 $ 1,000,000 $ 985,732 $ 981,585 (a) Carrying value of the senior notes represents principal amount less unamortized debt issuance costs and debt discounts. (b) See Note 1 for a discussion of fair value measurements. $1 Billion Facility . In July 2017, EQM amended and restated its credit facility to increase the borrowing capacity under the facility from $750 million to $1 billion and extend the term to July 2022. The $1 Billion Facility is available to fund working capital requirements and capital expenditures, to purchase assets, to pay distributions and repurchase units and for general partnership purposes (including purchasing assets from EQT and its subsidiaries and other third parties). Subject to certain terms and conditions, the $1 Billion Facility has an accordion feature that allows EQM to increase the available borrowings under the facility by up to an additional $500 million . In addition, the $1 Billion Facility includes a sublimit up to $100 million for same-day swing line advances and a sublimit up to $150 million for letters of credit. Further, EQM has the ability to request that one or more lenders make term loans to it under the $1 Billion Facility subject to the satisfaction of certain conditions, which term loans will be secured by cash and qualifying investment grade securities. EQM's obligations under the revolving portion of the $1 Billion Facility are unsecured. EQM is not required to maintain compensating bank balances under the $1 Billion Facility. EQM's debt issuer credit ratings, as determined by Standard and Poor's Ratings Services, Moody's Investors Service and Fitch Ratings Service on its non-credit-enhanced, senior unsecured long-term debt, determine the level of fees associated with its $1 Billion Facility in addition to the interest rate charged by the counterparties on any amounts borrowed against the lines of credit; the lower EQM's debt credit rating, the higher the level of fees and interest rate. During 2017 , 2016 and 2015 , the maximum amounts of EQM's outstanding borrowings under the credit facility at any time were $260 million , $401 million and $404 million , respectively, the average daily balances were approximately $74 million , $77 million and $261 million , respectively, and interest was incurred at weighted average annual interest rates of 2.8% , 2.0% and 1.7% , respectively. EQM had no letters of credit outstanding under its credit facility as of December 31, 2017 and 2016 . For the years ended December 31, 2017 , 2016 and 2015 , commitment fees of $1.8 million , $1.6 million and $1.2 million , respectively, were paid to maintain credit availability under the credit facility. EQM's $1 Billion Facility contains various provisions that, if not complied with, could result in termination of the credit facility, require early payment of amounts outstanding or similar actions. The most significant covenants and events of default relate to maintenance of a permitted leverage ratio, limitations on transactions with affiliates, limitations on restricted payments, insolvency events, nonpayment of scheduled principal or interest payments, acceleration of and certain other defaults under other financial obligations and change of control provisions. Under the $1 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). 364 -Day Facility . EQM has a $500 million , 364 -day, uncommitted revolving loan agreement with EQT that matures on October 24, 2018 and will automatically renew for successive 364 -day periods unless EQT delivers a non-renewal notice at least 60 days prior to the then current maturity date. EQM may terminate the 364 -Day Facility at any time by repaying in full the unpaid principal amount of all loans together with interest thereon. The 364 -Day Facility is available for general partnership purposes and does not contain any covenants other than the obligation to pay accrued interest on outstanding borrowings. Interest accrues on outstanding borrowings at an interest rate equal to the rate then applicable to similar loans under the $1 Billion Facility, or a successor revolving credit facility, less the sum of (i) the then applicable commitment fee under the $1 Billion Facility and (ii) 10 basis points. During the year ended December 31, 2017 , the maximum amount of EQM's outstanding borrowings under the 364 -Day Facility at any time was $100 million , the average daily balance was approximately $23 million and interest was incurred at a weighted average annual interest rate of 2.2% . There were no amounts outstanding at any time under the 364 -Day Facility in 2016. 4.125% Senior Notes . During the fourth quarter of 2016, EQM issued 4.125% Senior Notes due December 1, 2026 in the aggregate principal amount of $500 million . Net proceeds from the offering were used to repay the outstanding borrowings under the $1 Billion Facility at that time and for general partnership purposes. EQM's 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 December 31, 2017 , EQM was in compliance with all debt provisions and covenants.

Regulatory Assets and Liabiliti

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2017
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities	Regulatory Assets and Liabilities Regulatory assets and regulatory liabilities are recoverable or reimbursable over various periods and do not earn a return on investment. EQM believes that it will continue to be subject to rate regulation that will provide for the recovery or reimbursement of its regulatory assets and regulatory liabilities. Regulatory assets and regulatory liabilities are included in other assets and other long-term liabilities, respectively, in the accompanying consolidated balance sheets. As of December 31, 2017 2016 (Thousands) Regulatory assets: Deferred taxes (a) $ 13,076 $ 13,901 Other recoverable costs (b) 4,754 5,013 Total regulatory assets $ 17,830 $ 18,914 Regulatory liabilities: Deferred taxes (a) $ 10,488 $ — On-going post-retirement benefits other than pensions (c) 7,724 6,744 Other reimbursable costs 860 715 Total regulatory liabilities $ 19,072 $ 7,459 (a) The regulatory asset for deferred taxes primarily related to deferred income taxes recoverable through future rates on a historical deferred tax position and the equity component of AFUDC. The regulatory liability for deferred taxes relates to a revaluation of the historical difference between the regulatory and tax bases of regulated property, plant and equipment. EQM expects to recover the amortization of the deferred tax positions ratably over the corresponding life of the underlying assets that created the differences. Taxes on the equity component of AFUDC and the offsetting deferred income taxes will be collected through rates over the depreciable lives of the long-lived assets to which they relate. (b) Regulatory assets associated with other recoverable costs primarily related to the costs associated with the pension termination discussed in Note 14. (c) EQM defers expenses for on-going post-retirement benefits other than pensions which are subject to recovery in approved rates. The regulatory liability reflects lower cumulative actuarial expenses than the amounts recovered through rates.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes As a result of its limited partnership structure, EQM is not subject to federal and state income taxes. For federal and state income tax purposes, all income, expenses, gains, losses and tax credits generated by EQM flow through to EQM's unitholders; accordingly, EQM does not record a provision for income taxes. As discussed in Note 2, the October 2016 Acquisition and NWV Gathering Acquisition were transactions between entities under common control for which the consolidated financial statements of EQM have been retrospectively recast to reflect the combined entities. Accordingly, the income tax effects associated with these operations prior to acquisition are reflected in the consolidated financial statements as they were previously part of EQT's consolidated federal tax return. EQT's consolidated federal income tax was allocated among the group's members on a separate return basis with tax credits allocated to the members generating the credits. During the years ended December 31, 2016 and 2015 , net current and deferred income tax liabilities of approximately $94.0 million and $84.4 million , respectively, were eliminated through equity related to AVC, Rager, the Gathering Assets and NWV Gathering. The components of income tax expense (benefit) for the years ended December 31, 2016 and 2015 are as follows: Years Ended December 31, 2016 2015 (Thousands) Current: Federal $ 886 $ 12,960 State 487 985 Subtotal 1,373 13,945 Deferred: Federal 8,302 (30,931 ) State 472 245 Subtotal 8,774 (30,686 ) Total $ 10,147 $ (16,741 ) Income tax expense (benefit) differed from amounts computed at the federal statutory rate of 35% on pre-tax book income from continuing operations as follows: Years Ended December 31, 2016 2015 (Thousands) Tax at statutory rate $ 191,835 $ 153,435 Partnership income not subject to income taxes (182,455 ) (135,324 ) State income taxes 623 800 Regulatory assets 132 (35,685 ) Other 12 33 Income tax expense (benefit) $ 10,147 $ (16,741 ) Effective tax rate 1.9 % (3.8 )% For the year ended December 31, 2015, a tax benefit was realized by EQT in connection with a partial like-kind exchange of assets that resulted in tax deferral for EQT associated with AVC. The deferred taxes were eliminated through equity in 2016 along with the other current and deferred taxes associated with the October 2016 Acquisition. The fluctuations in income tax expense resulted primarily from the tax benefit realized by EQT in 2015 and the change in the tax status of AVC, Rager and the Gathering Assets in 2016 and NWV Gathering in 2015. EQM's historical uncertain tax positions related to the October 2016 Acquisition and NWV Gathering Acquisition were immaterial. EQT has indemnified EQM from and against any losses suffered or incurred by EQM and related to or arising out of or in connection with any federal, state or local income tax liabilities attributable to the ownership or operation of EQM's assets prior to the acquisition of such assets from EQT. Therefore, EQM does not anticipate any future liabilities arising from the historical deferred tax liabilities.

Concentrations of Credit Risk

Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Concentrations of Credit Risk	Concentrations of Credit Risk For the years ended December 31, 2017 , 2016 and 2015 , EQT accounted for approximately 73% , 75% and 73% , respectively, of EQM's total revenues. Additionally, for the years ended December 31, 2017 , 2016 and 2015 , PNG Companies, LLC and its affiliates accounted for approximately 12% , 12% and 14% of EQM's total revenues, respectively, all of which was included in the transmission segment. Approximately 40% and 47% of third party accounts receivable balances of $28.8 million and $20.7 million as of December 31, 2017 and 2016 , respectively, represent amounts due from marketers. EQM manages the credit risk of sales to marketers by limiting EQM's dealings to those marketers meeting specified criteria for credit and liquidity strength and by actively monitoring these accounts. EQM may request a letter of credit, guarantee, performance bond or other credit enhancement from a marketer in order for that marketer to meet EQM's credit criteria. EQM did not experience any significant defaults on accounts receivable during the years ended December 31, 2017 , 2016 and 2015 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies EQM is subject to federal, state and local environmental laws and regulations. These laws and regulations, which are constantly changing, can require expenditures for remediation and in certain instances result in assessment of fines. EQM has established procedures for ongoing evaluation of its operations to identify potential environmental exposures and assure compliance with regulatory requirements. The estimated costs associated with identified situations that require remedial action are accrued. However, when recoverable through regulated rates, certain of these costs are deferred as regulatory assets. Ongoing expenditures for compliance with environmental law and regulations, including investments in plant and facilities to meet environmental requirements, have not been material. Management believes that any such required expenditures will not be significantly different in either nature or amount in the future and does not know of any environmental liabilities that will have a material effect on its business, financial condition, results of operations, liquidity or ability to make distributions. In the ordinary course of business, various legal and regulatory claims and proceedings are pending or threatened against EQM. While the amounts claimed may be substantial, EQM is unable to predict with certainty the ultimate outcome of such claims and proceedings. EQM accrues legal and other direct costs related to loss contingencies when actually incurred. EQM has established reserves it believes to be appropriate for pending matters and, after consultation with counsel and giving appropriate consideration to available insurance, EQM believes that the ultimate outcome of any matter currently pending against EQM will not materially affect EQM's business, financial condition, results of operations, liquidity or ability to make distributions. See Note 6 for discussion of the MVP Joint Venture guarantee.

Postretirement Benefit Plans

Postretirement Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Postretirement Benefit Plans	Postretirement Benefit Plans Employees of EQT operate EQM's assets. EQT charges EQM for the payroll and benefit costs associated with these individuals and for retirees of Equitrans, the owner of EQM's FERC-regulated transmission, storage and gathering systems. EQT carries any obligations for employee-related benefits in its financial statements. EQT terminated the EQT Corporation Retirement Plan for Employees (the Retirement Plan), a defined benefit pension plan, effective December 31, 2014. On March 2, 2016, the IRS issued a favorable determination letter for the termination of the Retirement Plan. On June 28, 2016, EQT purchased annuities from and transferred the Retirement Plan assets and liabilities to American General Life Insurance Company. In the third quarter of 2016, EQM reimbursed EQT approximately $5.2 million for its proportionate share of such funding related to retirees of Equitrans. The settlement charge is expected to be recoverable in FERC approved rates and thus was recorded as a regulatory asset that will be amortized for rate recovery purposes over a period of 16 years. Equitrans' retirees participated in the Retirement Plan prior to its termination. Excluding the pension termination settlement payments described above, for the years ended December 31, 2016 and 2015 , EQM reimbursed EQT approximately $1.9 million and $0.4 million , respectively, for the funding of the Retirement Plan and was allocated expenses associated with the Retirement Plan of $0.1 million and $0.5 million , respectively. EQM contributes to a defined contribution plan sponsored by EQT. The contribution amount is a percentage of allocated base salary. In 2017 , 2016 and 2015 , EQM was charged its contribution percentage through the EQT payroll and benefit costs discussed in Note 5. EQM recognizes expenses for ongoing post-retirement benefits other than pensions, which are subject to recovery in the approved rates. Expenses recognized by EQM for the years ended December 31, 2017 , 2016 and 2015 for ongoing post-retirement benefits other than pensions were approximately $1.2 million each year.

Interim Financial Information (

Interim Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interim Financial Information (Unaudited)	Interim Financial Information (Unaudited) The following quarterly summary of operating results for the years ended December 31, 2017 and 2016 reflects variations due to the seasonal nature of the transmission and storage business. Three Months Ended March 31 June 30 September 30 December 31 (Thousands, except per unit amounts) 2017 Operating revenues $ 203,426 $ 198,966 $ 207,193 $ 224,511 Operating income 145,113 141,092 145,506 148,997 Net income $ 143,196 $ 139,139 $ 142,938 $ 146,631 Net income per limited partner unit: (a) Basic and diluted $ 1.36 $ 1.27 $ 1.28 $ 1.28 2016 Operating revenues $ 185,786 $ 178,042 $ 176,772 $ 195,014 Operating income 137,120 129,029 126,210 134,590 Net income $ 136,735 $ 131,859 $ 133,660 $ 135,700 Net income per limited partner unit: (a) Basic and diluted $ 1.39 $ 1.27 $ 1.23 $ 1.31 (a) Quarterly net income per limited partner unit amounts are stand-alone calculations and may not be additive to full-year amounts due to rounding and changes in outstanding units.

Summary of Operations and Sig23

Summary of Operations and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Basis of Presentation and Nature of Business	Organization and Basis of Presentation EQT Midstream Partners, LP and subsidiaries (collectively, EQM) is a growth-oriented Delaware limited partnership formed by EQT in January 2012. EQT Midstream Services, LLC (EQM General Partner) is a direct wholly owned subsidiary of EQT GP Holdings, LP (EQGP) and is the general partner of EQM. References in these consolidated financial statements to EQT refer collectively to EQT Corporation and its consolidated subsidiaries. As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast for all periods presented to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM on October 13, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control. EQM does not have any employees. Operational, management and other services for EQM are provided by employees of EQT and its subsidiaries. Nature of Business EQM is a growth-oriented limited partnership formed by EQT to own, operate, acquire and develop midstream assets in the Appalachian Basin. EQM provides midstream services to EQT and third parties in Pennsylvania, West Virginia and Ohio through two primary assets: the gathering system and the transmission and storage system. As of December 31, 2017 , EQM's gathering system included approximately 300 miles of high pressure gathering lines with approximately 2.3 Bcf per day of total firm contracted gathering capacity and multiple interconnect points with EQM's transmission and storage system. EQM's gathering system also includes approximately 1,500 miles of Federal Energy Regulatory Commission (FERC)-regulated low pressure gathering lines. Revenues are primarily generated from EQM's firm gathering contracts. As of December 31, 2017 , EQM's transmission and storage system included an approximately 950 -mile FERC-regulated interstate pipeline that connects to seven interstate pipelines and to local distribution companies. The transmission system is supported by 18 associated natural gas storage reservoirs with approximately 645 MMcf per day of peak withdrawal capacity and 43 Bcf of working gas capacity and 41 compressor units. As of December 31, 2017 , the transmission assets had total throughput capacity of approximately 4.4 Bcf per day. Revenues are primarily generated from EQM's firm transmission and storage contracts.
Principles of Consolidation	Principles of Consolidation : The consolidated financial statements include the accounts of all entities in which EQM holds a controlling financial interest. EQM applies the equity method of accounting where it can exert significant influence over, but does not control or direct the policies, decisions or activities of an entity. The consolidated financial statements reflect the pre-acquisition results of businesses acquired through common control transactions on a combined basis with EQM. See Note 2. Transactions between EQM and EQT have been identified in the consolidated financial statements as transactions between related parties and are discussed in Note 5.
Segments	Segments: Operating segments are revenue-producing components of the enterprise for which separate financial information is produced internally and are subject to evaluation by EQM's chief operating decision maker in deciding how to allocate resources. EQM reports its operations in two segments, which reflect its lines of business. Gathering primarily includes high pressure gathering lines and the FERC-regulated low pressure gathering system. Transmission includes EQM's FERC-regulated interstate pipeline and storage business. The operating segments are evaluated on their contribution to EQM's operating income. All of EQM's operating revenues, income from continuing operations and assets are generated or located in the United States. See Note 4.
Reclassification	Reclassification: Certain previously reported amounts have been reclassified to conform to the current year presentation.
Use of Estimates	Use of Estimates: The preparation of financial statements in conformity with United States generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents: EQM considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Interest earned on cash equivalents is included as a reduction to net interest expense in the accompanying statements of consolidated operations.
Trade and Other Receivables	Trade and Other Receivables: Trade and other receivables are stated at their historical carrying amount. Judgment is required to assess the ultimate realization of accounts receivable, including assessing the probability of collection and the creditworthiness of customers.
Fair Value of Financial Instruments	Fair Value of Financial Instruments: EQM has categorized its assets and liabilities disclosed at fair value into a three-level fair value hierarchy, based on the priority of the inputs to the valuation technique. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets and liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The carrying value 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; these are considered Level 1 fair values. The carrying value of EQM's credit facility borrowings approximates fair value as the interest rates are based on prevailing market rates; this is considered a Level 1 fair value. As EQM's senior notes are not actively traded, their fair value is a Level 2 fair value measurement estimated using a standard industry income approach model which utilizes a discount rate based on market rates for debt with similar remaining time to maturity and credit risk. See Note 9. The fair value of the Preferred Interest is a Level 3 fair value measurement which is estimated using an income approach model utilizing a market-based discount rate.
Property, Plant and Equipment	Property, Plant and Equipment: EQM's property, plant and equipment are stated at depreciated cost. Maintenance projects that do not increase the overall life of the related assets are expensed as incurred. Expenditures that extend the useful life of the underlying asset are capitalized. EQM capitalized internal costs of $46.5 million , $53.2 million and $78.9 million in 2017 , 2016 and 2015 , respectively. EQM capitalized interest of $4.1 million , $9.4 million and $5.6 million on assets under construction in 2017 , 2016 and 2015 , respectively, including the debt component of allowance for funds used during construction (AFUDC). As of December 31, 2017 2016 (Thousands) Gathering assets $ 1,526,028 $ 1,330,998 Accumulated depreciation (147,575 ) (110,473 ) Net gathering assets 1,378,453 1,220,525 Transmission and storage assets 1,674,080 1,563,860 Accumulated depreciation (248,474 ) (205,551 ) Net transmission and storage assets 1,425,606 1,358,309 Net property, plant and equipment $ 2,804,059 $ 2,578,834 Depreciation is recorded using composite rates on a straight-line basis over the estimated useful life of the assets. The overall rates of depreciation for the years ended December 31, 2017 , 2016 and 2015 were approximately 2.7% , 2.2% and 2.1% , respectively. EQM estimates pipelines have useful lives ranging from 20 years to 65 years and compression equipment has useful lives ranging from 20 years to 50 years . As circumstances warrant, depreciation estimates are reviewed to determine if any changes in the underlying assumptions are necessary. For EQM's regulated fixed assets, depreciation rates are re-evaluated each time it files with the FERC for a change in its transmission and storage rates. Whenever events or changes in circumstances indicate that the carrying amount of long-lived assets may not be recoverable, EQM reviews its long-lived assets for impairment by first comparing the carrying value of the assets to the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the assets. If the carrying value exceeds the sum of the assets' undiscounted cash flows, EQM estimates an impairment loss equal to the difference between the carrying value and fair value of the assets.
Investment in Unconsolidated Entity	Investment in Unconsolidated Entity: EQM evaluates its investment in unconsolidated entity for impairment whenever events or changes in circumstances indicate that the carrying value of the investment may have experienced a decline in value. When there is evidence of loss in value that is other than temporary, EQM compares the estimated fair value of the investment to the carrying value of the investment to determine whether impairment has occurred. If the estimated fair value is less than the carrying value, the excess of the carrying value over the estimated fair value is recognized as an impairment loss.
Unamortized Debt Discount and Issuance Expense	Unamortized Debt Discount and Issuance Expense: Discounts and expenses incurred with the issuance of EQM's senior notes are amortized over the term of the debt. These amounts are presented as a reduction of the debt on the accompanying consolidated balance sheets. Expenses incurred with the issuance and extension of EQM's $1 billion credit facility are presented in other assets on the accompanying consolidated balance sheets.
Natural Gas Imbalances	Natural Gas Imbalances: EQM experiences natural gas imbalances when the actual amount of natural gas delivered from a pipeline system or storage facility differs from the amount of natural gas scheduled to be delivered. EQM values these imbalances due to or from shippers and operators at current index prices. Imbalances are settled in-kind, subject to the terms of the FERC tariffs. Imbalances as of December 31, 2017 and 2016 were receivables of $5.2 million and $2.8 million , respectively, included in other current assets in the accompanying consolidated balance sheets with offsetting amounts recorded to system gas, a component of property, plant and equipment. EQM classifies imbalances as current as it expects to settle them within a year.
Asset Retirement Obligations	Asset Retirement Obligations: EQM is under no legal or contractual obligation to restore or dismantle its gathering system and transmission and storage system upon abandonment. Additionally, EQM operates and maintains its gathering system and transmission and storage system and it intends to do so as long as supply and demand for natural gas exists, which EQM expects for the foreseeable future. Therefore, EQM does not have any asset retirement obligations as of December 31, 2017 and 2016 .
Contingencies	Contingencies: EQM is involved in various regulatory and legal proceedings that arise in the ordinary course of business. A liability is recorded for contingencies based upon EQM's assessment that a loss is probable and that the amount of the loss can be reasonably estimated. EQM considers many factors in making these assessments, including history and specifics of each matter. Estimates are developed in consultation with legal counsel and are based upon the analysis of potential results. See Note 13.
Regulatory Accounting	Regulatory Accounting: EQM's regulated operations consist of interstate pipeline, intrastate gathering and storage operations subject to regulation by the FERC. Rate regulation provided by the FERC is designed to enable EQM to recover the costs of providing the regulated services plus an allowed return on invested capital. The application of regulatory accounting allows EQM to defer expenses and income in its consolidated balance sheets as regulatory assets and liabilities when it is probable that those expenses and income will be allowed in the rate setting process in a period different from the period in which they would have been reflected in the statements of consolidated operations for a non-regulated entity. The deferred regulatory assets and liabilities are then recognized in the statements of consolidated operations in the period in which the same amounts are reflected in rates. The amounts deferred in the consolidated balance sheets relate primarily to the accounting for income taxes and post-retirement benefit costs. EQM believes that it will continue to be subject to rate regulation that will provide for the recovery of deferred costs. See Note 10.
Revenue Recognition	Revenue Recognition: Reservation revenues on firm contracted capacity are recognized ratably over the contract period based on the contracted volume regardless of the amount of natural gas transported or gathered. Revenues associated with gathered or transported volumes under firm and interruptible contracts are recognized as physical deliveries of natural gas are made.
Allowance for Funds Used During Construction (AFUDC)	AFUDC: The carrying costs for the construction of certain long-lived regulated assets are capitalized and amortized over the related assets' estimated useful lives. The capitalized amount for construction of regulated assets includes interest cost (the debt component) and a designated cost of equity (the equity component) for financing the construction of these regulated assets.
Equity-Based Compensation	Equity-Based Compensation: EQM has awarded equity-based compensation in connection with the EQT Midstream Services, LLC 2012 Long-Term Incentive Plan. These awards will be paid in EQM common units; therefore, EQM treats these programs as equity awards. Awards are recorded at fair value which utilizes the published market price on the grant date. See Note 8.
Net Income per Limited Partner Unit	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. EQM's net income is allocated to the general partner and limited partners in accordance with their respective ownership percentages, and when applicable, giving effect to incentive distributions allocable to the general partner. The allocation of undistributed earnings, or net income in excess of distributions, to the incentive distribution rights (IDRs) is limited to available cash (as defined by EQM's partnership agreement) for the period. Any common units issued during the period are included on a monthly weighted-average basis for the periods in which they were outstanding. Diluted net income per limited partner unit reflects the potential dilution that could occur if securities or agreements to issue common units, such as awards under the long-term incentive plan, were exercised, settled or converted into EQM common units. When it is determined that potential common units resulting from an award subject to performance or market conditions should be included in the diluted net income per limited partner unit calculation, the impact is reflected by applying the treasury stock method. Net income attributable to AVC, Rager and the Gathering Assets for the periods prior to October 1, 2016 and to NWV Gathering for the periods prior to March 17, 2015 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 unitholders. The phantom units granted to the independent directors of the EQM General Partner will be paid in common units upon a director's termination of service on the EQM General Partner's Board of Directors. As there are no remaining service, performance or market conditions related to these awards, 20,959 , 17,196 and 14,017 phantom unit awards were included in the calculation of basic and diluted weighted average limited partner units outstanding for the years ended December 31, 2017 , 2016 and 2015 , respectively. Potentially dilutive securities included in the calculation of diluted weighted average limited partner units outstanding totaled zero , 20,548 and 160,633 for the years ended December 31, 2017 , 2016 and 2015 , respectively.
Income Taxes	Income Taxes: For federal and state income tax purposes, all income, expenses, gains, losses and tax credits generated flow through to EQM's unitholders; accordingly, there is no provision for income taxes for EQM. Net income for financial statement purposes may differ significantly from taxable income of unitholders because of differences between the tax basis and financial reporting basis of assets and liabilities and the taxable income allocation requirements under EQM's partnership agreement. The aggregate difference in the basis of EQM's net assets for financial and tax reporting purposes cannot be readily determined because information regarding each partner's tax attributes is not available to EQM. See Note 11.
Recently Issued Accounting Standards	Recently Issued Accounting Standards: In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers . The standard requires an entity to recognize revenue in a manner that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers - Deferral of the Effective Date which approved a one year deferral of ASU 2014-09 to annual reporting periods beginning after December 15, 2017. During the third quarter of 2017, EQM substantially completed its detailed review of the impact of the standard on each of its contracts. EQM adopted the ASUs using the modified retrospective method of adoption on January 1, 2018 and EQM did not require an adjustment to the opening balance of equity. EQM does not expect the standard to have a significant impact on its results of operations, liquidity or financial position in 2018. Additional disclosures will be required to describe the nature, amount, timing and uncertainty of revenue and cash flows from contracts with customers including disaggregation of revenue and remaining performance obligations. EQM implemented processes and controls to ensure new contracts are reviewed for the appropriate accounting treatment and to generate the disclosures required under the new standard in the first quarter of 2018. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities . The changes primarily affect the accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. This standard will eliminate the cost method of accounting for equity investments. The ASU will be effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period, with early adoption of certain provisions permitted. EQM will adopt this standard in the first quarter of 2018 and does not expect that the adoption will have a material impact on its financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases . The primary effect of adopting the new standard on leases will be to record assets and obligations for contracts currently recognized as operating leases. Lessees and lessors must apply a modified retrospective transition approach. The ASU will be effective for annual reporting periods beginning after December 15, 2018, including interim periods within that reporting period, with early adoption permitted. EQM has completed a high level identification of agreements covered by this standard and will continue to evaluate the impact this standard will have on its financial statements, internal controls and related disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments. This ASU 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 ASU eliminates the probable initial recognition threshold in current GAAP and, instead, requires an entity to reflect 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 that have the contractual right to receive cash. The ASU will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within that reporting period. EQM is currently evaluating the impact this standard will have on its financial statements and related disclosures. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments . This ASU addresses the presentation and classification of eight specific cash flow issues. The amendments in the ASU will be effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period, with early adoption permitted. EQM adopted this standard in the second quarter of 2017 with no material impact on its financial statements and related disclosures.
Subsequent Events	Subsequent Events: EQM has evaluated subsequent events through the date of the financial statement issuance.

Summary of Operations and Sig24

Summary of Operations and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property, Plant and Equipment	As of December 31, 2017 2016 (Thousands) Gathering assets $ 1,526,028 $ 1,330,998 Accumulated depreciation (147,575 ) (110,473 ) Net gathering assets 1,378,453 1,220,525 Transmission and storage assets 1,674,080 1,563,860 Accumulated depreciation (248,474 ) (205,551 ) Net transmission and storage assets 1,425,606 1,358,309 Net property, plant and equipment $ 2,804,059 $ 2,578,834
Regulated Revenues Net and Operating Expenses	The following tables present the total regulated operating revenues and expenses, and the regulated property, plant and equipment of EQM. Years Ended December 31, 2017 2016 2015 (Thousands) Operating revenues $ 390,883 $ 347,320 $ 309,984 Operating expenses $ 151,510 $ 118,611 $ 109,954
Schedule of Regulated Property, Plant and Equipment	As of December 31, 2017 2016 (Thousands) Property, plant & equipment $ 1,787,656 $ 1,675,433 Accumulated depreciation and amortization (278,756 ) (234,336 ) Net property, plant & equipment $ 1,508,900 $ 1,441,097

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Acquisitions	The following table presents EQM's acquisitions completed during the three years ended December 31, 2017 . Acquisition Date Total Consideration Cash Common Units Issued to EQT GP Units Issued to EQT (Thousands, except unit amounts) NWV Gathering Acquisition (a) 3/17/15 $ 925,683 $ 873,183 511,973 178,816 MVP Interest Acquisition (b) 3/30/15 54,229 54,229 — — Preferred Interest Acquisition (c) 4/15/15 124,317 124,317 — — October 2016 Acquisition (d) 10/13/16 $ 275,000 $ 275,000 — — (a) EQT contributed NWV Gathering to EQM Gathering Opco, LLC (EQM Gathering), an indirect wholly owned subsidiary of EQM. The cash portion of the purchase price was funded with net proceeds from an equity offering of EQM common units and borrowings under EQM's credit facility. (b) EQM assumed 100% of the membership interests in MVP Holdco, LLC (MVP Holdco), the owner of the interest (the MVP Interest) in the MVP Joint Venture, which at the time was an indirect wholly owned subsidiary of EQT. The cash payment made represented EQM's reimbursement to EQT for 100% of the capital contributions made by EQT to the MVP Joint Venture as of March 30, 2015. The cash payment was funded by borrowings under EQM's credit facility. See Note 6. (c) Pursuant to the NWV Gathering Acquisition contribution and sale agreement, EQM acquired the Preferred Interest from EQT in EES, which at the time was an indirect wholly owned subsidiary of EQT. EES generates revenue from services provided to a local distribution company. The cash payment was funded by borrowings under EQM's credit facility. In October 2016, the operating agreement of EES was amended to include mandatory redemption of the Preferred Interest at the end of the preference period, which is expected to be December 31, 2034. As a result of this amendment, the accounting for EQM's investment in EES converted from a cost method investment to a note receivable effective October 1, 2016. This conversion did not impact the carrying value of this instrument; however, distributions from EES subsequent to the amendment were recorded partly as a reduction in the Preferred Interest and partly as interest income, which is included in net interest expense in the accompanying statements of consolidated operations. Distributions received from EES prior to this amendment were included in other income in the accompanying statements of consolidated operations. (d) On October 13, 2016, EQM entered into a Purchase and Sale Agreement with EQT pursuant to which EQM acquired from EQT 100% of the outstanding limited liability company interests of AVC and Rager as well as the Gathering Assets. The closing occurred on October 13, 2016 and was effective as of October 1, 2016. The cash payment was funded by borrowings under EQM's credit facility.

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Public Offerings of Common Units	The following table summarizes EQM's public offerings of its common units during the three years ended December 31, 2017 . Common Units Issued GP Units Issued Price Per Unit Net Proceeds Underwriters' Discount and Other Offering Expenses (Thousands, except unit and per unit amounts) March 2015 equity offering (a) 9,487,500 25,255 $ 76.00 $ 696,582 $ 24,468 $750 Million At the Market (ATM) Program in 2015 (b) 1,162,475 — 74.92 85,483 1,610 November 2015 equity offering (c) 5,650,000 — 71.80 399,937 5,733 $750 Million ATM Program in 2016 (d) 2,949,309 — $ 74.42 $ 217,102 $ 2,381 (a) The underwriters exercised their option to purchase additional common units. The EQM General Partner purchased 25,255 EQM general partner units for approximately $1.9 million to maintain its then 2.0% general partner ownership percentage. This amount was included in net proceeds from this offering. The net proceeds were used to finance a portion of the cash consideration paid to EQT in connection with the NWV Gathering Acquisition as described in Note 2. (b) During the third quarter of 2015, EQM entered into an equity distribution agreement that established an ATM common unit offering program, pursuant to which a group of managers, acting as EQM's sales agents, may sell EQM common units having an aggregate offering price of up to $750 million (the $750 Million ATM Program). The price per unit represents an average price for all issuances under the $750 Million ATM Program in 2015. The underwriters' discount and other offering expenses in the table above include commissions of approximately $0.9 million . EQM used the net proceeds for general partnership purposes. Prior to this $750 Million ATM Program, the EQM General Partner maintained its general partner ownership percentage at the previous level of 2.0% . Starting with sales under the $750 Million ATM Program in 2015, the EQM General Partner elected not to maintain its general partner ownership percentage. (c) The net proceeds were used for general partnership purposes and to repay amounts outstanding under EQM's credit facility. (d) The price per unit represents an average price for all issuances under the $750 Million ATM Program in 2016. The underwriters' discount and other offering expenses in the table above include commissions of approximately $2.2 million . EQM used the net proceeds for general partnership purposes.
Summary of Common, Subordinated, and General Partner Units Issued	The following table summarizes EQM's common, subordinated and general partner units issued and outstanding during the three years ended December 31, 2017 . There were no issuances in 2017. Limited Partner Units General Common Subordinated Partner Units Total Balance at January 1, 2015 43,347,452 17,339,718 1,238,514 61,925,684 Conversion of subordinated units to common units 17,339,718 (17,339,718 ) — — 2014 EQM VDA issuance 21,063 — 430 21,493 March 2015 equity offering 9,487,500 — 25,255 9,512,755 NWV Gathering Acquisition consideration 511,973 — 178,816 690,789 $750 Million ATM Program 1,162,475 — — 1,162,475 November 2015 equity offering 5,650,000 — — 5,650,000 Balance at December 31, 2015 77,520,181 — 1,443,015 78,963,196 2014 EQM VDA issuance 19,796 — — 19,796 EQM Total Return Program issuance 92,472 — — 92,472 $750 Million ATM Program 2,949,309 — — 2,949,309 Balance at December 31, 2016 and 2017 80,581,758 — 1,443,015 82,024,773

Financial Information by Busi27

Financial Information by Business Segment (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Revenue from External Customers (Including Affiliates), Operating Income, and Reconciliation of Operating Income to Net Schedule of Revenue from External Customers (Including Affiliates), Operating Income, and Reconciliation of Operating Income to Net Income	Years Ended December 31, 2017 2016 2015 (Thousands) Revenues from external customers (including affiliates): Gathering $ 454,536 $ 397,494 $ 335,105 Transmission 379,560 338,120 297,831 Total operating revenues $ 834,096 $ 735,614 $ 632,936 Operating income: Gathering $ 333,563 $ 289,027 $ 243,257 Transmission 247,145 237,922 207,779 Total operating income $ 580,708 $ 526,949 $ 451,036 Reconciliation of operating income to net income: Other income 27,377 37,918 8,694 Net interest expense 36,181 16,766 21,345 Income tax expense (benefit) — 10,147 (16,741 ) Net income $ 571,904 $ 537,954 $ 455,126
Schedule of Segment Assets	As of December 31, 2017 2016 2015 (Thousands) Segment assets: Gathering $ 1,463,247 $ 1,292,713 $ 1,079,644 Transmission 1,487,501 1,413,631 1,183,641 Total operating segments 2,950,748 2,706,344 2,263,285 Headquarters, including cash 598,079 369,496 570,073 Total assets $ 3,548,827 $ 3,075,840 $ 2,833,358
Schedule of Depreciation, Amortization, and Expenditures for Segment Assets	Years Ended December 31, 2017 2016 2015 (Thousands) Depreciation and amortization: Gathering $ 38,796 $ 30,422 $ 24,360 Transmission 58,689 32,269 25,535 Total $ 97,485 $ 62,691 $ 49,895 Expenditures for segment assets: Gathering $ 196,871 $ 295,315 $ 225,537 Transmission 111,102 292,049 203,706 Total (a) $ 307,973 $ 587,364 $ 429,243 (a) 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 on the statements of consolidated cash flows until they are paid in a subsequent period. Accrued capital expenditures were approximately $33.1 million , $26.7 million , $24.1 million and $53.0 million at December 31, 2017 , 2016 , 2015 and 2014 , respectively.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Summary of Reimbursement Amounts and Affiliate Transactions	The following table summarizes the amounts and categories of expenses for which EQM was obligated to reimburse EQT pursuant to the omnibus agreement and the Secondment Agreement, as applicable, and the amounts and categories of obligations for which EQT was obligated to indemnify and/or reimburse EQM pursuant to the omnibus agreement for the years ended December 31, 2017 , 2016 and 2015 . Years Ended December 31, 2017 2016 2015 (Thousands) Reimbursements to EQT Operating and maintenance expense (a) $ 39,957 $ 33,526 $ 31,310 Selling, general and administrative expense (a) $ 67,424 $ 63,255 $ 46,149 Reimbursements from EQT (b) Plugging and abandonment $ 4 $ 195 $ 26 Bare steel replacement 15,704 — 6,268 Other capital reimbursements $ — $ 162 $ 1,198 (a) The expenses for which EQM reimburses EQT and its subsidiaries may not necessarily reflect the actual expenses that EQM would incur on a stand-alone basis, and EQM is unable to estimate what those expenses would be on a stand-alone basis. These amounts exclude the recast impact of the October 2016 Acquisition and NWV Gathering Acquisition as these amounts do not represent reimbursements pursuant to the omnibus agreement. (b) These reimbursements were recorded as capital contributions from EQT. Summary of Related Party Transactions . The following table summarizes related party transactions for the years ended December 31, 2017 , 2016 and 2015 . Years Ended December 31, 2017 2016 2015 (Thousands) Operating revenues $ 605,099 $ 551,353 $ 462,371 Operating and maintenance expense (a) 39,957 34,179 33,452 Selling, general and administrative expense (a) 67,424 67,345 55,092 Other income (b) 22,171 18,191 2,367 Interest income on Preferred Interest (see Note 2) 6,818 1,740 — Principal payments received on Preferred Interest (see Note 2) 4,166 1,024 — Distributions to EQM General Partner (c) 235,167 169,438 109,194 Capital contributions from EQT 15,463 602 7,492 Net contributions from/(distributions to) EQT $ — $ 20,234 $ (15,179 ) (a) The expenses for which EQM reimburses EQT and its subsidiaries may not necessarily reflect the actual expenses that EQM would incur on a stand-alone basis, and EQM is unable to estimate what those expenses would be on a stand-alone basis. These amounts include the recast impact of the October 2016 Acquisition and NWV Gathering Acquisition as they represent the total amounts allocated to EQM by EQT for the periods presented. (b) For the year ended December 31, 2017 , other income included equity income from the MVP Joint Venture of $22.2 million . For the year ended December 31, 2016 , other income included distributions received from EES of $8.3 million and equity income from the MVP Joint Venture of $9.9 million . For the year ended December 31, 2015 , other income included equity income from the MVP Joint Venture of $2.4 million . See Note 6. (c) The distributions to the EQM General Partner are based on the period to which the distributions relate and not the period in which the distributions were declared and paid. For example, for the year ended December 31, 2017 , total distributions to the EQM General Partner included the cash distribution declared on January 18, 2018 related to the fourth quarter 2017 of $1.025 per common unit and the amounts related to its general partner interest and IDRs. The following table summarizes related party balances as of December 31, 2017 and 2016 . As of December 31, 2017 2016 (Thousands) Accounts receivable – affiliate $ 103,304 $ 81,358 Due to related party 31,673 19,027 Investment in unconsolidated entity 460,546 184,562 Preferred Interest in EES (see Note 1) $ 119,127 $ 123,293

Investment in Unconsolidated 29

Investment in Unconsolidated Entity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	The following tables summarize the audited financial statements for the investment in unconsolidated entity accounted for under the equity method of accounting. Consolidated Balance Sheets As of December 31, 2017 2016 (Thousands) Current assets $ 330,271 $ 53,959 Noncurrent assets 747,728 361,820 Total assets $ 1,077,999 $ 415,779 Current liabilities $ 65,811 $ 10,149 Equity 1,012,188 405,630 Total liabilities and equity $ 1,077,999 $ 415,779 Statements of Consolidated Operations Years Ended December 31, 2017 2016 2015 (Thousands) AFUDC - equity $ 32,054 $ 16,315 $ 3,576 Net interest income 16,674 5,206 1,143 Net income $ 48,728 $ 21,521 $ 4,719

Cash Distributions (Tables)

Cash Distributions (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Cash Distributions to Unitholders	If for any quarter EQM has distributed available cash from operating surplus to the common unitholders in an amount equal to EQM's minimum quarterly distribution; then, EQM will distribute any additional available cash from operating surplus for that quarter among the unitholders and the EQM General Partner in the following manner: Total Quarterly Marginal Percentage Interest in Distributions Unit Target Amount Unitholders General Partner Minimum Quarterly Distribution $0.35 98.2% 1.8% First Target Distribution Above $0.3500 up to $0.4025 98.2% 1.8% Second Target Distribution Above $0.4025 up to $0.4375 85.2% 14.8% Third Target Distribution Above $0.4375 up to $0.5250 75.2% 24.8% Thereafter Above $0.5250 50.2% 49.8%

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Outstanding Debt	The following table presents EQM's outstanding debt as of December 31, 2017 and 2016 . December 31, 2017 December 31, 2016 Principal Carrying Value (a) Fair (b) Principal Carrying Value (a) Fair (b) (Thousands) $1 Billion Facility $ 180,000 $ 180,000 $ 180,000 $ — $ — $ — 364-Day Facility — — — — — — 4.00% Senior Notes due 2024 500,000 494,939 504,110 500,000 494,170 493,125 4.125% Senior Notes due 2026 500,000 492,413 501,990 500,000 491,562 488,460 Total debt $ 1,180,000 $ 1,167,352 $ 1,186,100 $ 1,000,000 $ 985,732 $ 981,585 (a) Carrying value of the senior notes represents principal amount less unamortized debt issuance costs and debt discounts. (b) See Note 1 for a discussion of fair value measurements.

Regulatory Assets and Liabili32

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Regulatory Assets and Liabilities Disclosure [Abstract]
Schedule of Regulatory Assets	Regulatory assets and regulatory liabilities are included in other assets and other long-term liabilities, respectively, in the accompanying consolidated balance sheets. As of December 31, 2017 2016 (Thousands) Regulatory assets: Deferred taxes (a) $ 13,076 $ 13,901 Other recoverable costs (b) 4,754 5,013 Total regulatory assets $ 17,830 $ 18,914 Regulatory liabilities: Deferred taxes (a) $ 10,488 $ — On-going post-retirement benefits other than pensions (c) 7,724 6,744 Other reimbursable costs 860 715 Total regulatory liabilities $ 19,072 $ 7,459 (a) The regulatory asset for deferred taxes primarily related to deferred income taxes recoverable through future rates on a historical deferred tax position and the equity component of AFUDC. The regulatory liability for deferred taxes relates to a revaluation of the historical difference between the regulatory and tax bases of regulated property, plant and equipment. EQM expects to recover the amortization of the deferred tax positions ratably over the corresponding life of the underlying assets that created the differences. Taxes on the equity component of AFUDC and the offsetting deferred income taxes will be collected through rates over the depreciable lives of the long-lived assets to which they relate. (b) Regulatory assets associated with other recoverable costs primarily related to the costs associated with the pension termination discussed in Note 14. (c) EQM defers expenses for on-going post-retirement benefits other than pensions which are subject to recovery in approved rates. The regulatory liability reflects lower cumulative actuarial expenses than the amounts recovered through rates.
Schedule of Regulatory Liabilities	Regulatory assets and regulatory liabilities are included in other assets and other long-term liabilities, respectively, in the accompanying consolidated balance sheets. As of December 31, 2017 2016 (Thousands) Regulatory assets: Deferred taxes (a) $ 13,076 $ 13,901 Other recoverable costs (b) 4,754 5,013 Total regulatory assets $ 17,830 $ 18,914 Regulatory liabilities: Deferred taxes (a) $ 10,488 $ — On-going post-retirement benefits other than pensions (c) 7,724 6,744 Other reimbursable costs 860 715 Total regulatory liabilities $ 19,072 $ 7,459 (a) The regulatory asset for deferred taxes primarily related to deferred income taxes recoverable through future rates on a historical deferred tax position and the equity component of AFUDC. The regulatory liability for deferred taxes relates to a revaluation of the historical difference between the regulatory and tax bases of regulated property, plant and equipment. EQM expects to recover the amortization of the deferred tax positions ratably over the corresponding life of the underlying assets that created the differences. Taxes on the equity component of AFUDC and the offsetting deferred income taxes will be collected through rates over the depreciable lives of the long-lived assets to which they relate. (b) Regulatory assets associated with other recoverable costs primarily related to the costs associated with the pension termination discussed in Note 14. (c) EQM defers expenses for on-going post-retirement benefits other than pensions which are subject to recovery in approved rates. The regulatory liability reflects lower cumulative actuarial expenses than the amounts recovered through rates.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Summary of Components of Income Tax Expense	The components of income tax expense (benefit) for the years ended December 31, 2016 and 2015 are as follows: Years Ended December 31, 2016 2015 (Thousands) Current: Federal $ 886 $ 12,960 State 487 985 Subtotal 1,373 13,945 Deferred: Federal 8,302 (30,931 ) State 472 245 Subtotal 8,774 (30,686 ) Total $ 10,147 $ (16,741 )
Summary of Income Tax Expense (Benefit)	Income tax expense (benefit) differed from amounts computed at the federal statutory rate of 35% on pre-tax book income from continuing operations as follows: Years Ended December 31, 2016 2015 (Thousands) Tax at statutory rate $ 191,835 $ 153,435 Partnership income not subject to income taxes (182,455 ) (135,324 ) State income taxes 623 800 Regulatory assets 132 (35,685 ) Other 12 33 Income tax expense (benefit) $ 10,147 $ (16,741 ) Effective tax rate 1.9 % (3.8 )%

Interim Financial Information34

Interim Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of Operating Results	The following quarterly summary of operating results for the years ended December 31, 2017 and 2016 reflects variations due to the seasonal nature of the transmission and storage business. Three Months Ended March 31 June 30 September 30 December 31 (Thousands, except per unit amounts) 2017 Operating revenues $ 203,426 $ 198,966 $ 207,193 $ 224,511 Operating income 145,113 141,092 145,506 148,997 Net income $ 143,196 $ 139,139 $ 142,938 $ 146,631 Net income per limited partner unit: (a) Basic and diluted $ 1.36 $ 1.27 $ 1.28 $ 1.28 2016 Operating revenues $ 185,786 $ 178,042 $ 176,772 $ 195,014 Operating income 137,120 129,029 126,210 134,590 Net income $ 136,735 $ 131,859 $ 133,660 $ 135,700 Net income per limited partner unit: (a) Basic and diluted $ 1.39 $ 1.27 $ 1.23 $ 1.31 (a) Quarterly net income per limited partner unit amounts are stand-alone calculations and may not be additive to full-year amounts due to rounding and changes in outstanding units.

Summary of Operations and Sig35

Summary of Operations and Significant Accounting Policies - Organization and Basis of Presentation and Nature of Business (Details)	12 Months Ended
	Dec. 31, 2017BcfBcf / dMMcf / dnatural_gas_storage_reservoircompressor_stationprimary_assetinterstate_pipelinemi
Segment Reporting Information [Line Items]
Number of primary assets through which services are provided | primary_asset	2
Transmission and Storage Assets
Segment Reporting Information [Line Items]
Length of FERC-regulated pipeline (in miles)	950
Number of interstate pipelines connected by FERC-regulated interstate pipeline system | interstate_pipeline	7
Number of associated natural gas storage reservoirs which supports FERC-regulated interstate pipeline system | natural_gas_storage_reservoir	18
Peak withdrawal capability per day of associated natural gas storage reservoirs (in MMcf per day) | MMcf / d	645
Working gas capacity of associated natural gas storage reservoirs (in Bcf) | Bcf	43
Number of compressor units | compressor_station	41
Total throughput capacity from transmission assets (in Bcf per day) | Bcf / d	4.4
Gathering System
Segment Reporting Information [Line Items]
Length of gathering lines (in miles)	300
Total firm gathering capacity (in Bcf per day) | Bcf / d	2.3
Length of FERC-regulated pipeline (in miles)	1,500

Summary of Operations and Sig36

Summary of Operations and Significant Accounting Policies - Significant Accounting Policies (Details)		12 Months Ended
		Dec. 31, 2017USD ($)segmentshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares
Property, Plant and Equipment [Line Items]
Number of segments | segment		2
Allowances for doubtful accounts		$ 446,000	$ 319,000
Other current assets (current portion of Preferred Interest in EES - see Note 1)		4,000,000	4,000,000
Internal costs capitalized		46,500,000	53,200,000	$ 78,900,000
Interest costs capitalized relative to the gathering assets		$ 4,100,000	$ 9,400,000	$ 5,600,000
Overall rate of depreciation		2.70%	2.20%	2.10%
Imbalances		$ 5,200,000	$ 2,800,000
Phantom unit awards (in shares) | shares	[1]	80,603,000	79,367,000	69,612,000
Interest Expense
Property, Plant and Equipment [Line Items]
AFUDC applicable to interest cost		$ 800,000	$ 2,400,000	$ 1,600,000
Other Income
Property, Plant and Equipment [Line Items]
AFUDC applicable to equity funds		$ 5,100,000	$ 19,400,000	$ 6,300,000
Pipelines
Property, Plant and Equipment [Line Items]
Pipeline's useful lives		40 years
Minimum | Pipelines
Property, Plant and Equipment [Line Items]
Pipeline's useful lives		20 years
Minimum | Compression Equipment
Property, Plant and Equipment [Line Items]
Pipeline's useful lives		20 years
Maximum | Pipelines
Property, Plant and Equipment [Line Items]
Pipeline's useful lives		65 years
Maximum | Compression Equipment
Property, Plant and Equipment [Line Items]
Pipeline's useful lives		50 years
Line of Credit
Property, Plant and Equipment [Line Items]
Credit facility		$ 1,000,000,000
PSUs
Property, Plant and Equipment [Line Items]
Phantom unit awards (in shares) | shares		20,959	17,196	14,017
Performance Shares and Phantom Share Units
Property, Plant and Equipment [Line Items]
Potentially dilutive securities (in shares) | shares		0	20,548	160,633
EES
Property, Plant and Equipment [Line Items]
Preferred Interest in EES		$ 119,127,000	$ 123,293,000
Fair Value, Inputs, Level 3 | EES | Estimate of Fair Value Measurement
Property, Plant and Equipment [Line Items]
Estimated fair value of Preferred Interest		$ 133,000,000	$ 132,000,000
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Summary of Operations and Sig37

Summary of Operations and Significant Accounting Policies - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 3,200,108	$ 2,894,858
Accumulated depreciation	(396,049)	(316,024)
Net property, plant and equipment	2,804,059	2,578,834
Gathering System
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,526,028	1,330,998
Accumulated depreciation	(147,575)	(110,473)
Net property, plant and equipment	1,378,453	1,220,525
Transmission and Storage Assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,674,080	1,563,860
Accumulated depreciation	(248,474)	(205,551)
Net property, plant and equipment	$ 1,425,606	$ 1,358,309

Summary of Operations and Sig38

Summary of Operations and Significant Accounting Policies - Schedule of Operating Revenues and Expenses (Details) - EQT Transmission - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Operating revenues	$ 390,883	$ 347,320	$ 309,984
Operating expenses	$ 151,510	$ 118,611	$ 109,954

Summary of Operations and Sig39

Summary of Operations and Significant Accounting Policies - Schedule of Regulated Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Property, plant & equipment	$ 1,787,656	$ 1,675,433
Accumulated depreciation and amortization	(278,756)	(234,336)
Net property, plant & equipment	$ 1,508,900	$ 1,441,097

Acquisitions - Schedule of Acqu

Acquisitions - Schedule of Acquisitions (Details) - USD ($) $ in Thousands	Oct. 13, 2016	Apr. 15, 2015	Mar. 30, 2015	Mar. 17, 2015	Dec. 31, 2015
NWV Gathering Acquisition
Business Acquisition [Line Items]
Total Consideration				$ 925,683
Cash				$ 873,183
Units issued to EQT (in shares)					690,789
NWV Gathering Acquisition | Common Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)				511,973	511,973
NWV Gathering Acquisition | GP Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)				178,816	178,816
MVP Holdco
Business Acquisition [Line Items]
Total Consideration			$ 54,229
Cash			$ 54,229
MVP Holdco | Common Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)			0
MVP Holdco | GP Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)			0
MVP Interest Acquisition
Business Acquisition [Line Items]
Membership interest (as a percent)			100.00%
Preferred Interest Acquisition
Business Acquisition [Line Items]
Total Consideration		$ 124,317
Cash		$ 124,317
Preferred Interest Acquisition | Common Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)		0
Preferred Interest Acquisition | GP Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)		0
October 2016 Acquisition
Business Acquisition [Line Items]
Total Consideration	$ 275,000
Cash	$ 275,000
Membership interest (as a percent)	100.00%
October 2016 Acquisition | Common Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)	0
October 2016 Acquisition | GP Units Issued to EQT
Business Acquisition [Line Items]
Units issued to EQT (in shares)	0
MVP Holdco
Business Acquisition [Line Items]
Membership interest (as a percent)			100.00%

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Recast
Property, Plant and Equipment [Line Items]
Increase in net income related to acquisition adjustment			$ 5.2	$ 4.2
Pipelines
Property, Plant and Equipment [Line Items]
Lease term	25 years
Useful life		40 years
Cumulative capital lease depreciation		$ 25.1

Equity - Schedule of Public Off

Equity - Schedule of Public Offerings of Common Units (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Units Issued (in shares)	5,650,000	9,512,755
Units Issued (ATM) (in shares)			2,949,309	1,162,475
Price Per Unit (in USD per share)	$ 71.80	$ 76	$ 74.42	$ 74.92
Net Proceeds	$ 399,937	$ 696,582	$ 217,102	$ 85,483
Underwriters' Discount and Other Offering Expenses	$ 5,733	$ 24,468	$ 2,381	$ 1,610
Limited Partner Units Common
Class of Stock [Line Items]
Units Issued (in shares)	5,650,000	9,487,500
Units Issued (ATM) (in shares)			2,949,309	1,162,475
General Partner Units
Class of Stock [Line Items]
Units Issued (in shares)	0	25,255
Units Issued (ATM) (in shares)			0	0

Equity - Schedule of Public O43

Equity - Schedule of Public Offering of Common Units, Footnotes (Details) - USD ($)	1 Months Ended			3 Months Ended	12 Months Ended
	Nov. 30, 2015	Mar. 31, 2015	Feb. 28, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Units Issued (in shares)	5,650,000	9,512,755
Ownership interest (as a percent)		2.00%	2.00%			2.00%
At the market program					$ 750,000,000	$ 750,000,000
Commissions				$ 900,000	$ 2,200,000
General Partner
Class of Stock [Line Items]
Units Issued (in shares)	0	25,255
Purchase amount of general partner units		$ 1,900,000

Equity - Schedule of Common, Su

Equity - Schedule of Common, Subordinated and General Partner Units (Details) - shares	Mar. 17, 2015	Feb. 29, 2016	Nov. 30, 2015	Mar. 31, 2015	Feb. 28, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)						78,963,196	61,925,684
Partner Units (in shares)						78,963,196	61,925,684
Conversion of subordinated units to common units (in shares)							0
Common units issued under 2014 EQM VDA issuance (in shares)						19,796	21,493
Equity offering (in shares)			5,650,000	9,512,755
Common units issued (in shares)						2,949,309	1,162,475
Ending balance (in shares)						82,024,773	78,963,196
NWV Gathering Acquisition consideration
Increase (Decrease) in Partners' Capital [Roll Forward]
Acquisition consideration (in shares)							690,789
Limited Partner Units Common
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)						77,520,181	43,347,452
Partner Units (in shares)						77,520,181	43,347,452
Conversion of subordinated units to common units (in shares)							17,339,718
Common units issued under 2014 EQM VDA issuance (in shares)		19,796			21,063	19,796	21,063
Equity offering (in shares)			5,650,000	9,487,500
Common units issued (in shares)						2,949,309	1,162,475
Ending balance (in shares)						80,581,758	77,520,181
Limited Partner Units Common | NWV Gathering Acquisition consideration
Increase (Decrease) in Partners' Capital [Roll Forward]
Acquisition consideration (in shares)	511,973						511,973
Limited Partner Units Subordinated
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)						0	17,339,718
Partner Units (in shares)						0	17,339,718
Conversion of subordinated units to common units (in shares)							(17,339,718)
Common units issued under 2014 EQM VDA issuance (in shares)						0	0
Equity offering (in shares)			0	0
Common units issued (in shares)						0	0
Ending balance (in shares)						0	0
Limited Partner Units Subordinated | NWV Gathering Acquisition consideration
Increase (Decrease) in Partners' Capital [Roll Forward]
Acquisition consideration (in shares)							0
General Partner Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in shares)						1,443,015	1,238,514
Partner Units (in shares)						1,443,015	1,238,514
Conversion of subordinated units to common units (in shares)							0
Common units issued under 2014 EQM VDA issuance (in shares)					430	0	430
Equity offering (in shares)			0	25,255
Common units issued (in shares)						0	0
Ending balance (in shares)						1,443,015	1,443,015
General Partner Units | NWV Gathering Acquisition consideration
Increase (Decrease) in Partners' Capital [Roll Forward]
Acquisition consideration (in shares)	178,816						178,816
EQM Total Return Programs
Increase (Decrease) in Partners' Capital [Roll Forward]
Common units issued under 2014 EQM VDA issuance (in shares)						92,472
EQM Total Return Programs | Limited Partner Units Common
Increase (Decrease) in Partners' Capital [Roll Forward]
Common units issued under 2014 EQM VDA issuance (in shares)		92,472				92,472
EQM Total Return Programs | Limited Partner Units Subordinated
Increase (Decrease) in Partners' Capital [Roll Forward]
Common units issued under 2014 EQM VDA issuance (in shares)						0
EQM Total Return Programs | General Partner Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Common units issued under 2014 EQM VDA issuance (in shares)						0
EQT Midstream Partners LP
Increase (Decrease) in Partners' Capital [Roll Forward]
Partner Units (in shares)								82,024,773
EQT Midstream Partners LP | Limited Partner Units Common
Increase (Decrease) in Partners' Capital [Roll Forward]
Partner Units (in shares)								80,581,758
EQT Midstream Partners LP | Limited Partner Units Subordinated
Increase (Decrease) in Partners' Capital [Roll Forward]
Partner Units (in shares)								0
EQT Midstream Partners LP | General Partner Units
Increase (Decrease) in Partners' Capital [Roll Forward]
Partner Units (in shares)								1,443,015

Equity - Narrative (Details)

Equity - Narrative (Details)		Feb. 17, 2015USD ($)	Feb. 29, 2016shares	Mar. 31, 2015	Feb. 28, 2015shares	Dec. 31, 2017shares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares
Class of Stock [Line Items]
Conversion of subordinated units to common units | $		$ 17,339,718						$ 0	[1],[2]
Subordinated units conversion to common unit ratio		1
Common units issued (in shares)							19,796	21,493
Ownership interest (as a percent)				2.00%	2.00%			2.00%
At the market program | $							$ 750,000,000	$ 750,000,000
EQT GP Holdings LP
Class of Stock [Line Items]
Partner interest (as a percent)						26.60%
EQT GP Holdings LP | EQT and Subsidiaries
Class of Stock [Line Items]
Ownership interest (as a percent)						100.00%
Partner interest (as a percent)						90.10%
Limited Partner Units Common
Class of Stock [Line Items]
Conversion of subordinated units to common units | $	[1],[2]							$ (939,431,000)
Common units issued (in shares)			19,796		21,063		19,796	21,063
Common units owned (in shares)						21,811,643
General Partner
Class of Stock [Line Items]
Common units issued (in shares)					430		0	430
Common units owned (in shares)						1,443,015
General Partner | EQT GP Holdings LP
Class of Stock [Line Items]
Ownership interest (as a percent)						1.80%
EQM Total Return Programs
Class of Stock [Line Items]
Common units issued (in shares)							92,472
EQM Total Return Programs | Limited Partner Units Common
Class of Stock [Line Items]
Common units issued (in shares)			92,472				92,472
EQM Total Return Programs | General Partner
Class of Stock [Line Items]
Common units issued (in shares)							0
[1]	All subordinated units were converted to common units on a one-for-one basis on February 17, 2015. For purposes of calculating net income per common and subordinated unit, the conversion of the subordinated units was deemed to have occurred on January 1, 2015. See Note 3.
[2]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Financial Information by Busi46

Financial Information by Business Segment - Schedule of Revenue from External Customers (Including Affiliates) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Revenues from external customers (including affiliates):
Total operating revenues		$ 224,511	$ 207,193	$ 198,966	$ 203,426	$ 195,014	$ 176,772	$ 178,042	$ 185,786	$ 834,096	[1],[2]	$ 735,614	[1],[2]	$ 632,936	[1],[2]
Operating income:
Total operating income		148,997	145,506	141,092	145,113	134,590	126,210	129,029	137,120	580,708	[1]	526,949	[1]	451,036	[1]
Reconciliation of operating income to net income:
Other income	[1],[3]									27,377		37,918		8,694
Net interest expense	[1],[4]									36,181		16,766		21,345
Income tax expense (benefit)	[1]									0		10,147		(16,741)
Net income		$ 146,631	$ 142,938	$ 139,139	$ 143,196	$ 135,700	$ 133,660	$ 131,859	$ 136,735	571,904	[1],[5],[6]	537,954	[1],[5],[6]	455,126	[1],[5],[6]
Operating Segments
Revenues from external customers (including affiliates):
Total operating revenues										834,096		735,614		632,936
Operating income:
Total operating income										580,708		526,949		451,036
Operating Segments | Gathering
Revenues from external customers (including affiliates):
Total operating revenues										454,536		397,494		335,105
Operating income:
Total operating income										333,563		289,027		243,257
Operating Segments | Transmission
Revenues from external customers (including affiliates):
Total operating revenues										379,560		338,120		297,831
Operating income:
Total operating income										$ 247,145		$ 237,922		$ 207,779
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	Operating revenues included affiliate revenues from EQT Corporation and subsidiaries (collectively, EQT) of $605.1 million, $551.4 million and $462.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.
[3]	For the year ended December 31, 2017, other income included equity income from Mountain Valley Pipeline, LLC (MVP Joint Venture) of $22.2 million. For the year ended December 31, 2016, other income included distributions received from EQT Energy Supply, LLC (EES) of $8.3 million and equity income from the MVP Joint Venture of $9.9 million. For the year ended December 31, 2015, other income included equity income from the MVP Joint Venture of $2.4 million. See Note 6.
[4]	For the years ended December 31, 2017 and 2016, net interest expense included interest income on the preferred interest (the Preferred Interest) in EES of $6.8 million and $1.7 million, respectively.
[5]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[6]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Financial Information by Busi47

Financial Information by Business Segment - Schedule of Segment Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment assets:
Total assets	$ 3,548,827	$ 3,075,840	$ 2,833,358
Operating Segments
Segment assets:
Total assets	2,950,748	2,706,344	2,263,285
Operating Segments | Gathering
Segment assets:
Total assets	1,463,247	1,292,713	1,079,644
Operating Segments | Transmission
Segment assets:
Total assets	1,487,501	1,413,631	1,183,641
Headquarters, including cash
Segment assets:
Total assets	$ 598,079	$ 369,496	$ 570,073

Financial Information by Busi48

Financial Information by Business Segment - Schedule of Depreciation, Amortization and Expenditures for Segment Assets (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Depreciation and amortization:
Total	[1],[2]	$ 97,485	$ 62,691	$ 49,895
Expenditures for segment assets:
Accrued capital expenditures		33,100	26,700	24,100	$ 53,000
Operating Segments
Depreciation and amortization:
Total		97,485	62,691	49,895
Expenditures for segment assets:
Total		307,973	587,364	429,243
Operating Segments | Gathering
Depreciation and amortization:
Total		38,796	30,422	24,360
Expenditures for segment assets:
Total		196,871	295,315	225,537
Operating Segments | Transmission
Depreciation and amortization:
Total		58,689	32,269	25,535
Expenditures for segment assets:
Total		$ 111,102	$ 292,049	$ 203,706
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Related Party Transactions - Sc

Related Party Transactions - Schedule of Reimbursement Amounts (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reimbursements to EQT
Operating and maintenance expense	[1],[2]		$ 84,717	$ 73,213	$ 70,103
Selling, general and administrative expense	[1],[2]		71,186	72,761	61,902
EQT
Reimbursements from EQT
Other capital reimbursements		$ 5,200
EQT | Omnibus Agreement
Reimbursements to EQT
Operating and maintenance expense			39,957	33,526	31,310
Selling, general and administrative expense			67,424	63,255	46,149
Reimbursements from EQT
Plugging and abandonment			4	195	26
Bare steel replacement			15,704	0	6,268
Other capital reimbursements			$ 0	$ 162	$ 1,198
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	Operating and maintenance expense included charges from EQT of $40.0 million, $34.2 million and $33.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Selling, general and administrative expense included charges from EQT of $67.4 million, $67.3 million and $55.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.

Related Party Transactions - Su

Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands		Jan. 18, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Operating and maintenance expense	[1],[2]		$ 84,717	$ 73,213	$ 70,103
Selling, general and administrative expense	[1],[2]		71,186	72,761	61,902
Other income			22,171	18,191	2,367
Distributions to the EQM General Partner			235,167	169,438	109,194
Capital contributions from EQT	[3]		15,463	602	7,492
Equity income	[4]		22,171	9,898	2,367
EQT and Subsidiaries
Related Party Transaction [Line Items]
Operating revenues			605,100	551,400	462,400
Operating and maintenance expense			39,957	34,179	33,452
Selling, general and administrative expense			67,424	67,345	55,092
EES
Related Party Transaction [Line Items]
Interest expense on Preferred Interest			6,818	1,740	0
Principal payments received on the Preferred Interest			4,166	1,024	0
EQT
Related Party Transaction [Line Items]
Capital contributions from EQT			15,463	602	7,492
Net contributions from/(distributions to) EQT			0	20,234	(15,179)
Subsequent Event
Related Party Transaction [Line Items]
Cash distribution declared per common unit (in USD per share)		$ 1.025
Variable Interest Entity, Not Primary Beneficiary | EES
Related Party Transaction [Line Items]
Distributions included in other income				8,300
Other income | Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture
Related Party Transaction [Line Items]
Equity income			$ 22,200	$ 9,900	$ 2,400
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	Operating and maintenance expense included charges from EQT of $40.0 million, $34.2 million and $33.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Selling, general and administrative expense included charges from EQT of $67.4 million, $67.3 million and $55.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.
[3]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[4]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Related Party Transactions - 51

Related Party Transactions - Summary of Related Party Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Accounts receivable – affiliate	$ 103,304	$ 81,358
Due to related party	31,673	19,027
Investment in unconsolidated entity	460,546	184,562
EES
Related Party Transaction [Line Items]
Preferred Interest in EES	$ 119,127	$ 123,293

Investment in Unconsolidated 52

Investment in Unconsolidated Entity (Details) $ in Thousands		Mar. 30, 2015USD ($)mi	Feb. 28, 2018USD ($)	Jan. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jan. 31, 2016	Oct. 31, 2015	Apr. 30, 2015
Schedule of Equity Method Investments [Line Items]
Equity income	[1]					$ 22,171	$ 9,898	$ 2,367
MVP
Schedule of Equity Method Investments [Line Items]
Length of pipeline (in miles) | mi		300
Variable Interest Entity, Not Primary Beneficiary | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership interest sold (as a percent)									8.50%
Variable Interest Entity, Not Primary Beneficiary | MVP
Schedule of Equity Method Investments [Line Items]
Issuance of performance guarantee					$ 91,000	$ 91,000
MVP Joint Venture | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Ownership amount		$ 54,200
Ownership interest sold (as a percent)										1.00%	10.00%
Ownership interest (as a percent)					45.50%	45.50%
Capital call notice					$ 105,700
Maximum financial statement exposure					$ 552,000	$ 552,000
MVP Joint Venture | Variable Interest Entity, Not Primary Beneficiary | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Ownership amount				$ 27,200
MVP Joint Venture | Variable Interest Entity, Not Primary Beneficiary | Scenario, Forecast | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Ownership amount			$ 78,500
Other income | MVP Joint Venture | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Equity income						$ 22,200	$ 9,900	$ 2,400
Beneficial Owner | MVP Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)					66.67%	66.67%
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Investment in Unconsolidated 53

Investment in Unconsolidated Entity - Schedule of Unaudited Condensed Financial Statements for the Investment in Unconsolidated Equity (Details) - MVP Joint Venture - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Consolidated Balance Sheets
Current assets	$ 330,271	$ 53,959
Noncurrent assets	747,728	361,820
Total assets	1,077,999	415,779
Current liabilities	65,811	10,149
Equity	1,012,188	405,630
Total liabilities and equity	1,077,999	415,779
Condensed Statements of Consolidated Operations
AFUDC - equity	32,054	16,315	$ 3,576
Net interest income	16,674	5,206	1,143
Net income	$ 48,728	$ 21,521	$ 4,719

Cash Distributions - Narrative

Cash Distributions - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 18, 2018	Mar. 31, 2015	Feb. 28, 2015	Dec. 31, 2017	Dec. 31, 2015
Distribution Made to Limited Partner [Line Items]
Threshold period for partnership agreement				45 days
Ownership interest (as a percent)		2.00%	2.00%		2.00%
Incentive distribution rights				$ 41.1
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Cash distribution declared per common unit (in USD per share)	$ 1.025
General Partner
Distribution Made to Limited Partner [Line Items]
Percentage of quarterly distributions 1				13.00%
Percentage of quarterly distributions 2				23.00%
Percentage of quarterly distributions 3				48.00%
Cash distribution declared				$ 2.2
General Partner | EQT GP Holdings LP
Distribution Made to Limited Partner [Line Items]
Ownership interest (as a percent)				1.80%
Limited Partner
Distribution Made to Limited Partner [Line Items]
Cash distribution declared				$ 22.4

Cash Distributions - Schedule o

Cash Distributions - Schedule of Distribution of Available Cash from Operating Surplus (Details)	12 Months Ended
	Dec. 31, 2017$ / shares
Distribution Made to Limited Partner [Line Items]
Minimum Quarterly Distribution (in USD per share)	$ 0.35
Unitholders
Distribution Made to Limited Partner [Line Items]
Minimum Quarterly Distribution (as a percent)	98.20%
First Target Distribution (as a percent)	98.20%
Second Target Distribution (as a percent)	85.20%
Third Target Distribution (as a percent)	75.20%
Thereafter (as a percent)	50.20%
General Partner
Distribution Made to Limited Partner [Line Items]
Minimum Quarterly Distribution (as a percent)	1.80%
First Target Distribution (as a percent)	1.80%
Second Target Distribution (as a percent)	14.80%
Third Target Distribution (as a percent)	24.80%
Thereafter (as a percent)	49.80%
Minimum | Unitholders
Distribution Made to Limited Partner [Line Items]
Total Quarterly Distribution per Unit Target Amount in First Target Distribution, Maximum (in USD per share)	$ 0.3500
Total Quarterly Distribution per Unit Target Amount in Second Target Distribution, Maximum (in USD per share)	0.4025
Total Quarterly Distribution per Unit Target Amount in Third Target Distribution, Maximum (in USD per share)	0.4375
Total Quarterly Distribution per Unit Target Amount in Subsequent Target Distribution, Minimum (in USD per share)	0.5250
Maximum | Unitholders
Distribution Made to Limited Partner [Line Items]
Total Quarterly Distribution per Unit Target Amount in First Target Distribution, Maximum (in USD per share)	0.4025
Total Quarterly Distribution per Unit Target Amount in Second Target Distribution, Maximum (in USD per share)	0.4375
Total Quarterly Distribution per Unit Target Amount in Third Target Distribution, Maximum (in USD per share)	$ 0.5250

Equity-Based Compensation Plan

Equity-Based Compensation Plan (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based compensation expense recorded by the Company
Equity-based compensation expense	$ 0.2	$ 0.2	$ 0.2
EQM Total Return Programs
Share-based compensation expense recorded by the Company
Equity-based compensation expense			0.7
2014 EQM VDA
Share-based compensation expense recorded by the Company
Equity-based compensation expense			$ 0.6
Phantom Units
Share-based compensation expense recorded by the Company
Performance awards (in shares)	21,739
Common units (in shares)	2,940	2,610	2,220
Grant date fair value (in USD per share)	$ 76.68	$ 75.46	$ 88

Debt - Schedule of Outstanding

Debt - Schedule of Outstanding Debt (Details) - USD ($)	Oct. 26, 2016	Dec. 31, 2017	Jul. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Principal		$ 1,180,000,000		$ 1,000,000,000
Line of Credit
Debt Instrument [Line Items]
Credit facility		1,000,000,000
Line of Credit | One Billion Credit Facility
Debt Instrument [Line Items]
Credit facility		$ 1,000,000,000	$ 1,000,000,000
Senior Notes | 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Senior notes interest rate (as a percent)		4.00%
Principal		$ 500,000,000		$ 500,000,000
Senior Notes | 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Senior notes interest rate (as a percent)		4.125%		4.125%
Principal		$ 500,000,000		$ 500,000,000
$1 Billion Facility
Debt Instrument [Line Items]
Principal		$ 180,000,000		0
$1 Billion Facility | 364-Day Facility
Debt Instrument [Line Items]
Expiration period	364 days
Credit facility	$ 500,000,000
Line of Credit | $1 Billion Facility | 364-Day Facility
Debt Instrument [Line Items]
Expiration period		364 days
Credit facility		$ 0		0
Carrying Value
Debt Instrument [Line Items]
Total debt		1,167,352,000		985,732,000
Carrying Value | Senior Notes | 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Senior Notes outstanding		494,939,000		494,170,000
Carrying Value | Senior Notes | 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Senior Notes outstanding		492,413,000		491,562,000
Carrying Value | $1 Billion Facility
Debt Instrument [Line Items]
Facility outstanding		180,000,000		0
Carrying Value | Line of Credit | $1 Billion Facility | 364-Day Facility
Debt Instrument [Line Items]
Facility outstanding		0		0
Fair Value
Debt Instrument [Line Items]
Total debt		1,186,100,000		981,585,000
Fair Value | Senior Notes | 4.00% Senior Notes due 2024
Debt Instrument [Line Items]
Senior Notes outstanding		504,110,000		493,125,000
Fair Value | Senior Notes | 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Senior Notes outstanding		501,990,000		488,460,000
Fair Value | $1 Billion Facility
Debt Instrument [Line Items]
Facility outstanding		180,000,000		0
Fair Value | Line of Credit | $1 Billion Facility | 364-Day Facility
Debt Instrument [Line Items]
Facility outstanding		$ 0		$ 0

Debt - $1 Billion Facility (Det

Debt - $1 Billion Facility (Details)	1 Months Ended	12 Months Ended
	Jul. 31, 2017USD ($)lender	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jun. 30, 2017USD ($)
Line of Credit Facility [Line Items]
Credit facility borrowings		$ 180,000,000	$ 0
Credit Facility
Line of Credit Facility [Line Items]
Credit facility		1,000,000,000
Commitment fees		1,800,000	1,600,000	$ 1,200,000
Same-day Swing Line Advances
Line of Credit Facility [Line Items]
Credit facility	$ 100,000,000
Letter of Credit
Line of Credit Facility [Line Items]
Credit facility	150,000,000
$1 Billion Facility | One Billion Credit Facility
Line of Credit Facility [Line Items]
Credit facility borrowings		0	0
Credit Facility | One Billion Credit Facility
Line of Credit Facility [Line Items]
Credit facility	1,000,000,000	1,000,000,000
Increase in available borrowings under the facility (up to)	$ 500,000,000
Maximum amount of outstanding short-term loans		260,000,000	401,000,000	404,000,000
Average daily balance of short-term loans outstanding		$ 74,000,000	$ 77,000,000	$ 261,000,000
Weighted average annual interest rate (as a percent)		2.80%	2.00%	1.70%
Consolidated leverage ratio (not more than)	5
Consolidated leverage ratio for certain measurement periods (not more than)	5.50
Credit Facility | Seven Hundred and Fifty Million Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility					$ 750,000,000
Minimum | Credit Facility
Line of Credit Facility [Line Items]
Number of lenders | lender	1

Debt - 364-Day Facility (Detail

Debt - 364-Day Facility (Details) - USD ($)	Oct. 26, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2017
Line of Credit | $1 Billion Facility
Line of Credit Facility [Line Items]
Basis points	0.10%
Line of Credit
Line of Credit Facility [Line Items]
Credit facility		$ 1,000,000,000
364-Day Facility | $1 Billion Facility
Line of Credit Facility [Line Items]
Expiration period	364 days
Credit facility	$ 500,000,000
Renewal notice period	60 days
Maximum amount of outstanding short-term loans		100,000,000
Average daily balance of short-term loans outstanding		$ 23,000,000
Weighted average annual interest rate (as a percent)		2.20%
Amounts outstanding			$ 0
364-Day Facility | Line of Credit | $1 Billion Facility
Line of Credit Facility [Line Items]
Expiration period		364 days
Credit facility		$ 0	0
Line of Credit | One Billion Credit Facility
Line of Credit Facility [Line Items]
Credit facility		1,000,000,000			$ 1,000,000,000
Maximum amount of outstanding short-term loans		260,000,000	401,000,000	$ 404,000,000
Average daily balance of short-term loans outstanding		$ 74,000,000	$ 77,000,000	$ 261,000,000
Weighted average annual interest rate (as a percent)		2.80%	2.00%	1.70%

Debt - 4.125% Senior Notes (Det

Debt - 4.125% Senior Notes (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Principal	$ 1,180,000,000	$ 1,000,000,000
Senior Notes | 4.125% Senior Notes due 2026
Debt Instrument [Line Items]
Senior notes interest rate (as a percent)	4.125%	4.125%
Principal	$ 500,000,000	$ 500,000,000

Regulatory Assets and Liabili61

Regulatory Assets and Liabilities - Regulatory Assets (Details) - Other Assets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Regulatory assets:
Total regulatory assets	$ 17,830	$ 18,914
Deferred taxes
Regulatory assets:
Total regulatory assets	13,076	13,901
Other recoverable costs
Regulatory assets:
Total regulatory assets	$ 4,754	$ 5,013

Regulatory Assets and Liabili62

Regulatory Assets and Liabilities - Regulatory Liabilities (Details) - Other Liabilities - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Regulatory liabilities:
Total regulatory liabilities	$ 19,072	$ 7,459
Deferred taxes
Regulatory liabilities:
Total regulatory liabilities	10,488	0
On-going post-retirement benefits other than pensions
Regulatory liabilities:
Total regulatory liabilities	7,724	6,744
Other reimbursable costs
Regulatory liabilities:
Total regulatory liabilities	$ 860	$ 715

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Federal statutory rate (as a percent)	35.00%
AVC, Rager, the Gathering Assets, NWV Gathering
Business Acquisition [Line Items]
Net current and deferred income tax liabilities		$ 94	$ 84.4

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal			$ 886	$ 12,960
State			487	985
Subtotal			1,373	13,945
Deferred:
Federal			8,302	(30,931)
State			472	245
Subtotal	[1]	$ 0	8,774	(30,686)
Total	[2]	$ 0	$ 10,147	$ (16,741)
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate			$ 191,835	$ 153,435
Partnership income not subject to income taxes			(182,455)	(135,324)
State income taxes			623	800
Regulatory assets			132	(35,685)
Other			12	33
Total	[1]	$ 0	$ 10,147	$ (16,741)
Effective tax rate			1.90%	(3.80%)
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.

Concentrations of Credit Risk (

Concentrations of Credit Risk (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentrations of Credit Risk
Accounts receivable balances	$ 28,804	$ 20,662
Revenue | Customer Concentration
Concentrations of Credit Risk
Percentage of total revenues	12.00%	12.00%	14.00%
Accounts Receivable | Customer Concentration
Concentrations of Credit Risk
Percentage of total revenues	40.00%	47.00%
EQT | Revenue | Customer Concentration
Concentrations of Credit Risk
Percentage of total revenues	73.00%	75.00%	73.00%

Postretirement Benefit Plans (D

Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension and Other Postretirement Benefit Plans
Regulatory asset amortization period	16 years
Defined Benefit Pension Plan
Pension and Other Postretirement Benefit Plans
Amount reimbursed			$ 1.9	$ 0.4
Expenses allocated			0.1	0.5
Other Post-Employment Benefit Plans
Pension and Other Postretirement Benefit Plans
Retirement benefits other than pensions		$ 1.2	$ 1.2	$ 1.2
EQT
Pension and Other Postretirement Benefit Plans
Reimbursement of funding related to retirees	$ 5.2

Interim Financial Information68

Interim Financial Information (Unaudited) - Summary of Operating Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	[1]	Dec. 31, 2016	[1]	Dec. 31, 2015	[1]
Quarterly Financial Information Disclosure [Abstract]
Operating revenues	$ 224,511	$ 207,193	$ 198,966	$ 203,426	$ 195,014	$ 176,772	$ 178,042	$ 185,786	$ 834,096	[2]	$ 735,614	[2]	$ 632,936	[2]
Operating income	148,997	145,506	141,092	145,113	134,590	126,210	129,029	137,120	580,708		526,949		451,036
Net income	$ 146,631	$ 142,938	$ 139,139	$ 143,196	$ 135,700	$ 133,660	$ 131,859	$ 136,735	$ 571,904	[3],[4]	$ 537,954	[3],[4]	$ 455,126	[3],[4]
Net income per limited partner unit:
Basic (in USD) per share	$ 1.28	$ 1.28	$ 1.27	$ 1.36	$ 1.31	$ 1.23	$ 1.27	$ 1.39	$ 5.19		$ 5.21		$ 4.71
Diluted (in USD per share)	$ 1.28	$ 1.28	$ 1.27	$ 1.36	$ 1.31	$ 1.23	$ 1.27	$ 1.39	$ 5.19		$ 5.21		$ 4.70
[1]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of the Allegheny Valley Connector, LLC (AVC), Rager Mountain Storage Company LLC (Rager) and certain gathering assets (the Gathering Assets), which were acquired by EQM effective on October 1, 2016 (the October 2016 Acquisition), and the Northern West Virginia Marcellus gathering system (NWV Gathering), which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[2]	Operating revenues included affiliate revenues from EQT Corporation and subsidiaries (collectively, EQT) of $605.1 million, $551.4 million and $462.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.
[3]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.
[4]	As discussed in Note 2, EQM's consolidated financial statements have been retrospectively recast to include the pre-acquisition results of AVC, Rager and the Gathering Assets, which were acquired by EQM effective on October 1, 2016, and NWV Gathering, which was acquired by EQM on March 17, 2015, because these transactions were between entities under common control.