CNX Midstream Partners (CNXM) 10-K 7 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 07, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CNX Midstream Partners LP
Entity Central Index Key	1,610,418
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		63,651,896
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 813.3

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Gathering revenue — related party	$ 167,048	$ 184,693	$ 239,211
Gathering revenue — third party	89,620	49,155	0
Total Revenue	256,668	233,848	239,211
Expenses
Operating expense — related party	19,814	25,513	29,771
Operating expense — third party	27,343	26,640	30,405
General and administrative expense — related party	13,867	10,750	10,446
General and administrative expense — third party	8,595	5,717	5,384
Loss on asset sales	2,501	3,914	10,083
Depreciation expense	21,939	22,692	21,201
Interest expense	23,614	4,560	1,799
Total Expense	117,673	99,786	109,089
Net Income	138,995	134,062	130,122
Less: Net income attributable to noncontrolling interest	4,953	19,069	33,636
Net Income Attributable to General and Limited Partner Ownership Interest in CNX Midstream Partners LP	134,042	114,993	96,486
Less: General partner interest in net income, including incentive distribution rights	13,387	5,614	2,526
Limited partner interest in net income	$ 120,655	$ 109,379	$ 93,960
Net income per limited partner unit - basic (in USD per unit)	$ 1.90	$ 1.72	$ 1.59
Net income per limited partner unit — diluted (in USD per unit)	$ 1.89	$ 1.72	$ 1.58
Weighted average limited partner units outstanding - basic (in units)	63,635	63,582	59,207
Weighted average limited partner units outstanding — diluted (in units)	63,694	63,634	59,289

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current Assets:
Cash	$ 3,966	$ 3,194
Receivables — related party	17,073	13,104
Receivables — third party	7,028	8,251
Other current assets	2,383	2,169
Total Current Assets	30,450	26,718
Property and Equipment (Note 6):
Property and equipment	974,394	972,841
Less — accumulated depreciation	82,619	73,563
Property and Equipment — Net	891,775	899,278
Other assets	3,203	593
TOTAL ASSETS	925,428	926,589
Current Liabilities:
Trade accounts payable	9,401	6,925
Accrued interest payable	7,761	87
Accrued liabilities	26,757	16,590
Due to related party (Note 5)	4,980	2,376
Total Current Liabilities	48,899	25,978
Other Liabilities:
Revolving credit facility (Note 7)	84,000	149,500
Long-term debt (Note 8)	393,215	0
Total Other Liabilities	477,215	149,500
Total Liabilities	526,114	175,478
Partners’ Capital and Noncontrolling Interest:
General partner interest	10,900	4,328
Partners’ capital attributable to CNX Midstream Partners LP	331,443	393,755
Noncontrolling interest	67,871	357,356
Total Partners’ Capital and Noncontrolling Interest	399,314	751,111
TOTAL LIABILITIES AND PARTNERS’ CAPITAL	925,428	926,589
Common Units
Partners’ Capital and Noncontrolling Interest:
Limited partners' capital	$ 320,543	$ 389,427

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2018	Dec. 31, 2017
Common Units
Units issued (in units)	63,639,676	63,588,152
Units outstanding (in units)	63,639,676	63,588,152

Consolidated Statements Of Part

Consolidated Statements Of Partners' Capital And Noncontrolling Interest - USD ($) $ in Thousands		Total	Partners’ CapitalLimited PartnersCommon Units	Partners’ CapitalLimited PartnersSubordinated Units	Partners’ CapitalGeneral Partner	Capital Attributable to Partners	Noncontrolling Interest
Partners' capital, beginning balance at Dec. 31, 2015		$ 803,142	$ 399,399	$ (82,900)	$ (3,389)	$ 313,110	$ 490,032
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		130,122	47,935	46,025	2,526	96,486	33,636
Investments by partners and General Partner and noncontrolling interest holder activity		(9,065)			3	3	(9,068)
Quarterly distributions to unitholders		(59,690)	(29,128)	(29,111)	(1,451)	(59,690)
Acquisition of remaining 25% interest in Anchor System		(140,000)	(606)			(606)	(139,394)
Unit-based compensation		775	775			775
Vested units withheld for unitholder taxes		(23)	(23)			(23)
Partners' capital, ending balance at Dec. 31, 2016		725,261	418,352	(65,986)	(2,311)	350,055	375,206
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		134,062	72,215	37,164	5,614	114,993	19,069
Investments by partners and General Partner and noncontrolling interest holder activity		(36,889)			30	30	(36,919)
Quarterly distributions to unitholders		(77,117)	(39,544)	(33,514)	(4,059)	(77,117)
Partners' capital amount. exchange and conversations	[1]		(62,336)	62,336
Noncash contribution of assets held by general partner		5,054			5,054	5,054
Unit-based compensation		1,176	1,176			1,176
Vested units withheld for unitholder taxes		(436)	(436)			(436)
Partners' capital, ending balance at Dec. 31, 2017		751,111	389,427	0	4,328	393,755	357,356
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		138,995	120,655		13,387	134,042	4,953
Investments by partners and General Partner and noncontrolling interest holder activity		(3,505)			20	20	(3,525)
Quarterly distributions to unitholders		(94,044)	(84,104)		(9,940)	(94,044)
Acquisition of Shirley-Penns System		(265,000)	(153,587)			(153,587)	(111,413)
Partners' capital amount. exchange and conversations		(133,411)	46,089			46,089	(179,500)
Noncash contribution of assets held by general partner		3,105			3,105	3,105
Unit-based compensation		2,411	2,411			2,411
Vested units withheld for unitholder taxes		(348)	(348)			(348)
Partners' capital, ending balance at Dec. 31, 2018		$ 399,314	$ 320,543	$ 0	$ 10,900	$ 331,443	$ 67,871
[1]	All subordinated units were converted to common units on a one-for-one basis on November 15, 2017. For purposes of calculating net income per common and subordinated unit, the conversion of the subordinated units was deemed to have occurred on October 1, 2017. See Note 4.

Consolidated Statements Of Pa_2

Consolidated Statements Of Partners' Capital And Noncontrolling Interest (Parenthetical)	Nov. 15, 2017	Dec. 31, 2016	Nov. 16, 2016
Anchor Systems
Limited partner controlling interest acquired, percentage		25.00%	25.00%
Subordinated Units
Conversion ratio	100.00%

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 138,995	$ 134,062	$ 130,122
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense and amortization of debt issuance costs	23,540	22,860	21,364
Unit-based compensation	2,411	1,176	775
Loss on long-term asset sales	2,501	3,914	10,083
Other	388	771	695
Changes in assets and liabilities:
Due to/from affiliate	(1,580)	3,376	13,885
Receivables — third party	1,223	(8,251)	0
Other current and non-current assets	475	162	(144)
Accounts payable and other accrued liabilities	12,162	(2,520)	(16,691)
Net Cash Provided by Operating Activities	180,115	155,550	160,089
Cash Flows from Investing Activities:
Capital expenditures	(145,331)	(48,366)	(50,660)
Proceeds from sale of assets	6,462	21,531	5,332
Net Cash Used in Investing Activities	(138,869)	(26,835)	(45,328)
Cash Flows from Financing Activities:
Distributions to general partner and noncontrolling interest holders, net	(3,505)	(36,889)	(2,344)
Quarterly distributions to unitholders	(94,044)	(77,117)	(59,690)
Net payments on unsecured $250.0 million credit facility	(149,500)	(17,500)
Net payments on unsecured $250.0 million credit facility			93,500
Net borrowings on secured $600.0 million credit facility	84,000	0	0
Proceeds from issuance of long-term debt, net of discount	394,000	0	0
Debt issuance costs	(6,077)	0	0
Vested units withheld for unitholder taxes	(348)	(436)	(23)
Net Cash Used in Financing Activities	(40,474)	(131,942)	(108,557)
Net Increase (Decrease) in Cash	772	(3,227)	6,204
Cash at Beginning of Period	3,194	6,421	217
Cash at End of Period	3,966	3,194	6,421
Cash Paid During the Period For:
Interest	15,283	4,437	1,921
Noncash Investing Activities:
Accrued capital expenditures	19,118	9,942	3,471
Anchor Systems
Cash Flows from Financing Activities:
Acquisition payments to noncontrolling interest	0	0	(140,000)
Shirley-Penns System
Cash Flows from Financing Activities:
Acquisition payments to noncontrolling interest	$ (265,000)	$ 0	$ 0

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical)	Dec. 31, 2018USD ($)
Unsecured Debt | Revolving Credit Facility
Revolving credit facility	$ 250,000,000
Secured Debt | Revolving Credit Facility
Revolving credit facility	$ 600,000,000

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	DESCRIPTION OF BUSINESS CNX Midstream Partners LP (the “Partnership”, or “we”, “us”, or “our”) is a growth-oriented master limited partnership focused on the ownership, operation, development and acquisition of natural gas gathering and other midstream energy assets to service our customers’ production in the Marcellus Shale and Utica Shale in Pennsylvania and West Virginia. Our assets include natural gas gathering pipelines and compression and dehydration facilities, as well as condensate gathering, collection, separation and stabilization facilities. We are managed by our general partner, CNX Midstream GP LLC (the “general partner”), a wholly owned subsidiary of CNX Gathering LLC (“CNX Gathering”). CNX Gathering is a wholly owned subsidiary of CNX Resources Corporation (NYSE: CNX)(“CNX Resources”). On January 3, 2018, CNX Gas Company LLC (“CNX Gas”), an indirect wholly owned subsidiary of CNX Resources, acquired from NBL Midstream, LLC (“NBL Midstream”), a wholly owned subsidiary of Noble Energy, Inc. (“Noble Energy”), NBL Midstream’s 50% membership interest in CNX Gathering for cash consideration of $305.0 million and the mutual release of all outstanding claims between the parties (the “General Partner Transaction”). As a result of the General Partner Transaction, CNX Resources owns 100% of the membership interest in CNX Gathering and is the sole sponsor of the Partnership. Accordingly, we may refer to CNX Resources as the “Sponsor” throughout this Annual Report on Form 10-K. Following the General Partner Transaction, Noble Energy owned 21,692,198 common units representing limited partner interests in the Partnership (the “Retained Units”). Noble Energy executed an underwritten public offering of 7,475,000 of its Retained Units on June 29, 2018 and executed private securities sale agreements with multiple buyers for the remaining 14,217,198 Retained Units on September 26, 2018. The Partnership did not receive any proceeds as a result of Noble Energy’s sale of its Retained Units. Following the September 26, 2018 sale, Noble Energy has no remaining interests in the Partnership. Description of Business Our midstream assets consist of two operating segments that we refer to as our “Anchor Systems,” and “Additional Systems” based on their relative current cash flows, growth profiles, capital expenditure requirements and the timing of their development. • Our Anchor Systems, in which the Partnership owns a 100% controlling interest, include our most developed midstream systems that generate the largest portion of our current cash flows, including our four primary midstream systems (the McQuay, Majorsville, Mamont and Shirley-Penns Systems), a 20” high-pressure pipeline contributed to us in the CNX Transaction and related assets. • Our Additional Systems, in which the Partnership owns a 5% controlling interest, include several gathering systems primarily located in the wet gas regions of our dedicated acreage. Revenues from our Additional Systems are currently derived primarily from the Pittsburgh Airport area. Currently, the substantial majority of capital investment in these systems would be funded by CNX Resources in proportion to CNX Gathering’s 95% retained ownership interest. As a result of the CNX and HG Energy Transactions (described below), the Partnership distributed its ownership interests in (i) our “Growth Systems,” which were primarily located in the dry gas regions of our dedicated acreage in central West Virginia, and (ii) in the Moundsville area assets formerly within the Additional Systems, to CNX Gathering. CNX Gathering subsequently transferred these assets to HG Energy. In order to maintain operational flexibility, our operations are conducted through, and our operating assets are owned by, our operating subsidiaries. However, neither we nor our operating subsidiaries have any employees. Our general partner has the sole responsibility for providing the personnel necessary to conduct our operations, whether through directly hiring employees or by obtaining the services of others, which may include personnel of CNX Resources as provided through contractual relationships with the Partnership. All of the personnel who conduct our business are employed or contracted by our general partner and its affiliates, including our Sponsor, but we sometimes refer to these individuals as our employees because they provide services directly to us. See Note 5–Related Party Transactions for additional information. Transactions with our Sponsor and HG Energy II Appalachia, LLC On May 3, 2018, we announced a strategic transaction with our Sponsor, pursuant to which we amended our gas gathering agreement (“GGA”) with CNX to provide for the following (collectively, the “CNX Transactions”): • Dedication to the Partnership of approximately 16,100 additional Utica acres in our Anchor Systems; • Commitment to develop 40 additional wells in the Anchor Systems by 2023, subject to the terms of the GGA; • Contribution to the Anchor Systems of a 20” high pressure pipeline in addition to a one-time payment to us of approximately $2.0 million in cash; and • Distribution of our 5% interest in the Growth Systems and related assets, as well as our 5% interest in the Moundsville midstream assets that were a part of the Additional Systems, to CNX Gathering, which subsequently transferred these assets to HG Energy II Appalachia, LLC (“HG Energy”). On May 3, 2018, we also announced a strategic transaction with HG Energy, pursuant to which we amended our GGA with HG Energy to provide for the following (collectively, the “HG Energy Transaction”): • Release from dedication of approximately 18,000 acres, net to the Partnership, which was comprised of approximately 275,000 acres (or approximately 14,000 acres, net to the Partnership) within the Growth and Additional Systems and approximately 4,200 scattered acres located in the Anchor Systems; • Removal of our obligation to provide gathering services or make capital investments in the Growth Systems or in the Moundsville area of the Additional Systems; and • Commitment by HG Energy to develop 12 additional wells in the Anchor Systems by 2021, subject to the terms of the HG Energy GGA. Following the CNX and HG Energy Transactions, the aggregate number of Anchor Systems well commitments to the Partnership increased from 140 wells over the course of the next five years to 192 wells. The non-cash distribution of our interests in these assets to CNX Gathering resulted in a reduction to property and equipment, net of $133.4 million , a reduction in noncontrolling interests of $179.5 million and an increase to partners’ capital of $46.1 million . At December 31, 2018, the Partnership has no remaining interests in the Growth Systems or the Moundsville area assets that were historically included within the Additional Systems. Acquisition of Shirley-Penns System At December 31, 2017, CNX Gathering owned a 95% noncontrolling interest, while the Partnership owned the remaining 5% controlling interest, in the Additional Systems, which owned the gathering system and related assets commonly referred to as the Shirley-Penns System. On March 16, 2018, the Partnership acquired the remaining 95% interest in the Shirley-Penns System, pursuant to which the Additional Systems transferred its interest in the Shirley-Penns System on a pro rata basis to CNX Gathering and the Partnership in accordance with each transferee’s respective ownership interest in the Additional Systems. Following such transfer, CNX Gathering sold its aggregate interest in the Shirley-Penns System, which now resides in the Anchor Systems, in exchange for cash consideration in the amount of $265.0 million (the “Shirley-Penns Acquisition”). The Partnership funded the Shirley-Penns Acquisition with a portion of the proceeds from the issuance of 6.5% senior notes due 2026 (the “Senior Notes”). Acquisition of Remaining Interests in the Anchor Systems On November 16, 2016, the Partnership acquired the remaining 25% noncontrolling interest in the Anchor Systems from CNX Gathering (the “Anchor Systems Acquisition”) in exchange for (i) cash consideration in the amount of $140.0 million , (ii) the Partnership’s issuance of 5,183,154 common units at an issue price of $20.42 per common unit, calculated as the volume-weighted average trading price of the common units over the trailing 20-day trading period ending on November 11, 2016, and (iii) the Partnership’s issuance to the general partner of an additional interest in the Partnership in an amount necessary for our general partner to maintain its two percent general partner interest in the Partnership. The cash consideration was distributed and the Unit Consideration issued 50% to CNX Gas and 50% to NBL Midstream. Noble Energy Sale of Upstream Assets On June 28, 2017, Noble Energy sold its upstream assets in northern West Virginia and southern Pennsylvania to HG Energy, effectively making HG Energy the new shipper on the dedicated acreage that was previously owned by Noble Energy (the “Noble Energy Asset Sale”). The Partnership currently gathers the natural gas and condensate volumes produced by HG Energy on our dedicated acreage under the terms of our gathering agreement with Noble Energy, which was assigned to HG Energy upon consummation of the Noble Energy Asset Sale and further amended in connection with the HG Energy Transaction.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Use of Estimates The accompanying audited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and various disclosures. Actual results could differ from those estimates, which are evaluated on an ongoing basis, utilizing historical experience and other methods considered reasonable under the particular circumstances. Although these estimates are based on management’s best available knowledge at the time, changes in facts and circumstances or discovery of new facts or circumstances may result in revised estimates and actual results may differ from these estimates. Effects on the Partnership’s business, financial position and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revision become known. In the opinion of management, all adjustments considered necessary for a fair presentation of the accompanying consolidated financial statements have been recorded. Principles of Consolidation The consolidated financial statements include the accounts of the Partnership and all of its controlled subsidiaries, including 100% of each of the Anchor Systems, Growth Systems and Additional Systems in the relevant periods. Although the Partnership has less than a 100% economic interest in the Growth and Additional Systems, each were consolidated fully with the results of the Partnership. However, after adjusting for noncontrolling interests, net income attributable to general and limited partner ownership interests in the Partnership reflect only that portion of net income that is attributable to the Partnership’s unitholders. For example, as a result of the Anchor Systems Acquisition, net income attributable to general and limited partner ownership interests in the Partnership includes 100% of the results of the Anchor Systems for the period subsequent to the closing date of that transaction. In addition, net income attributable to general and limited partner ownership interests in the Partnership includes 100% of the results of the Shirley-Penns Systems for the period subsequent to the closing date of that transaction. Transactions between the Partnership, CNX and Noble Energy have been identified in the consolidated financial statements as transactions between related parties in the relevant periods and are discussed in Note 5–Related Party Transactions. Jumpstart Our Business Startups Act ( “ JOBS Act ” ) Under the JOBS Act, for as long as the Partnership remained an “emerging growth company” as defined in the JOBS Act, we were able to take advantage of certain exemptions from the Securities and Exchange Commission’s (“SEC”) reporting requirements that are applicable to other public companies that are not emerging growth companies, including not being required to provide an auditor’s attestation report on management’s assessment of the effectiveness of its system of internal control over financial reporting pursuant to Section 404 of the Sarbanes-Oxley Act, reduced disclosure obligations regarding executive compensation in our periodic reports, and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and seeking unitholder approval of any golden parachute payments not previously approved. At December 31, 2018 , the Partnership is no longer an emerging growth company pursuant to the JOBS Act, as the market value of limited partner interests held by non-affiliates was in excess of $700 million at June 30, 2018, and we became a large accelerated filer as defined under the Securities Exchange Act of 1934. Accordingly, among other things, we are required to provide an auditor’s attestation report on management’s assessment of the effectiveness of its system of internal control over financial reporting pursuant to Section 404 of the Sarbanes-Oxley Act in this Annual Report on Form 10-K and more fulsome executive compensation information required by Item 402 of Regulation S-K, including Compensation Discussions and Analysis, for the year ended December 31, 2018. Revenue Recognition On January 1, 2018, the Partnership adopted Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers and all the related amendments (“new revenue standard”) using the modified retrospective method. We did not have a transition adjustment as a result of the adoption of the new revenue standard. Revenues from contracts with customers We record revenue when obligations under the terms of the contracts with our shippers are satisfied; generally this occurs on a daily basis as we gather gas at the wellhead. Revenue is measured as the amount of consideration we expect to receive in exchange for providing the natural gas gathering services. Nature of performance obligations At contract inception, we assess the services promised in our contracts with customers and identify a performance obligation for each promised service that is distinct. To identify the performance obligations, we consider all of the services promised in the contract, regardless of whether they are explicitly stated or are implied by customary business practices. Our revenue is generated from natural gas gathering activities. The gas gathering services are interruptible in nature and include charges for the volume of gas actually gathered and do not guarantee access to the system. Volumetric-based fees relate to actual volumes gathered. In general, the interruptible gathering of each unit (MMBtu) of natural gas represents a separate performance obligation. Payment terms for these contracts require payment within 25 days of the end of the calendar month in which the hydrocarbons are gathered. Transaction price allocated to remaining performance obligations The new revenue standard requires that we disclose the aggregate amount of transaction price that is allocated to performance obligations that have not yet been satisfied. However, the guidance provides certain practical expedients that limit this requirement. Substantially all of our revenues are derived from contracts with CNX Resources and HG Energy that have terms of greater than one year. Under these contracts, the interruptible gathering of each unit of natural gas represents a separate performance obligation. For revenue associated with the Shirley-Penns System, for which we have a contract with remaining performance obligations, the aggregate amount of the transaction price allocated to remaining performance obligations was $401.3 million at December 31, 2018. We expect to recognize minimum revenue of $21.4 million and $34.7 million , respectively, during the years ending December 31, 2019 and December 31, 2020 under the MVC. The amount of revenue associated with this contract up to the minimum volume commitment (“MVC”) is fixed in nature, and volumes that we may gather above the MVC will be variable in nature. As of December 31, 2018, no future performance obligations exist relative to volumes to be gathered in excess of the MVC as the related volumes have not yet been nominated for gathering. Therefore, we have not disclosed the value of unsatisfied performance obligations for the variable aspect of this agreement, nor have we disclosed the value of other unsatisfied performance obligations that are variable in nature. Prior-period performance obligations We record revenue when obligations under the terms of the contracts with our shippers are satisfied; generally this occurs on a daily basis when we gather gas at the wellhead. In some cases, we are required to estimate the amount of natural gas that we have gathered during an accounting period and record any differences between our estimates and the actual units of natural gas that we gathered in the following month. We have existing internal controls for our revenue estimation process and related accruals; historically, any identified differences between our revenue estimates and actual revenue received have not been significant. For the years ended December 31, 2018 and 2017, revenue recognized in the reporting period related to performance obligations satisfied in prior reporting periods was not material. Disaggregation of revenue See Note 10–Segment Information for additional information. Contract balances We invoice customers once our performance obligations have been satisfied, at which point payment becomes unconditional. Accordingly, our contracts with customers do not give rise to contract assets or liabilities under the new revenue standard. We also have no contract assets recognized from the costs. Classification The fees we charge our affiliates, including our Sponsor, are recorded in gathering revenue — related party in our consolidated statements of operations. Related party fees also included those charged to Noble Energy through the date of the Noble Energy Asset Sale. Fees from midstream services we perform for HG Energy, and any other third party shipper, are recorded in gathering revenue — third party in our consolidated statements of operations. Cash Cash includes cash on hand and on deposit at banking institutions. Receivables Receivables are recorded at the invoiced amount and do not bear interest. When applicable, we reserve for specific accounts receivable when it is probable that all or a part of an outstanding balance will not be collected, such as customer bankruptcies. Collectability is determined based on terms of sale, credit status of customers and various other circumstances. We regularly review collectability and establish or adjust the reserve as necessary using the specific identification method. Account balances are charged off against the reserve after all means of collection have been exhausted and the potential for recovery is considered remote. There were no reserves for uncollectable amounts at December 31, 2018 or 2017 . Fair Value Measurement The Financial Accounting Standards Board (the “FASB”) Accounting Standards Codification Topic 820, Fair Value Measurements and Disclosures, clarifies the definition of fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements. This guidance also relates to all nonfinancial assets and liabilities that are not recognized or disclosed on a recurring basis (e.g., the initial recognition of asset retirement obligations and impairments of long‑lived assets). The fair value is the price that we estimate we would receive upon selling an asset or that we would pay to transfer a liability in an orderly transaction between market participants at the measurement date. A fair value hierarchy is used to prioritize input to valuation techniques used to estimate fair value. An asset or liability subject to the fair value requirements is categorized within the hierarchy based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. The highest priority (Level 1) is given to unadjusted quoted market prices in active markets for identical assets or liabilities, and the lowest priority (Level 3) is given to unobservable inputs. Level 2 inputs are data, other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly. The carrying values on our balance sheet of our current assets, current liabilities and revolving credit facility approximate fair values due to their short maturities. We estimate the fair value of our long-term debt, which is not actively traded, using a standard industry income approach model that utilizes a discount rate based on market rates for other debt with a similar remaining time to maturity and credit risk (Level 2). The estimated fair value of our long-term debt was approximately $380.0 million at December 31, 2018. Property and Equipment Property and equipment is recorded at cost upon acquisition and is depreciated on a straight-line basis over the assets’ estimated useful lives or over their lease terms of the assets. Expenditures which extend the useful lives of existing property and equipment are capitalized. When properties are retired or otherwise disposed, the related cost and accumulated depreciation are removed from the respective accounts and any profit or loss on disposition is recognized as a gain or loss. The Partnership evaluates whether long-lived assets have been impaired and have processes in place to ensure that we become aware of such indicators. Impairment indicators include, but are not limited to, sustained decreases in commodity prices, a decline in customer well results and lower throughput forecasts, and increases in construction or operating costs. For such long-lived assets, impairment exists when the carrying amount of an asset or group of assets exceeds our estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset or group of assets. If the carrying amount of the long-lived asset(s) is not recoverable, based on the estimated future undiscounted cash flows, the impairment loss would be measured as the excess of the asset’s carrying amount over its estimated fair value. In the event that impairment indicators exist, we conduct an impairment test. Fair value represents the estimated price between market participants to sell an asset in the principal or most advantageous market for the asset, based on assumptions a market participant would make. When warranted, management assesses the fair value of long-lived assets using commonly accepted techniques and may use more than one source in making such assessments. Sources used to determine fair value include, but are not limited to, recent third-party comparable sales, internally developed discounted cash flow analyses, and analyses from outside advisors. Significant changes, such as the condition of an asset or management’s intent to utilize the asset, generally require management to reassess the cash flows related to long-lived assets. No property and equipment impairments were identified during the periods presented in the accompanying consolidated financial statements. Environmental Matters We are subject to various federal, state and local laws and regulations relating to the protection of the environment. Environmental expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations, and do not contribute to current or future revenue generation, are expensed. Liabilities are recorded when environmental assessments and/or clean-ups are probable, and the costs can be reasonably estimated. At this time, we are unable to assess the timing and/or effect of potential liabilities related to greenhouse gas emissions or other environmental issues. As of December 31, 2018 and 2017 , we had no material environmental matters that required the recognition of a separate liability or specific disclosure. Asset Retirement Obligations Our gathering pipelines and compressor stations have an indeterminate life. If properly maintained, they will operate for an indeterminate period as long as supply and demand for natural gas exists, which we expect for the foreseeable future. We are under no legal or contractual obligation to restore or dismantle our gathering system upon abandonment. Therefore, we have no recorded liabilities for asset retirement obligations at December 31, 2018 or 2017 . Variable Interest Entities Each of the Anchor and Additional Systems, and our former Growth Systems (the “ Limited Partnerships”) is also a limited partnership and a variable interest entity ( “ VIE”). These VIEs correspond with the manner in which we report our segment information in Note 10–Segment Information, which also includes information regarding the Partnership’s involvement with each of these VIEs and their relative contributions to our financial position, operating results and cash flows. The Partnership fully consolidates each of the Limited Partnerships through its ownership of the Operating Company, which, through its general partner ownership interest in each of the Limited Partnerships, is considered to be the primary beneficiary for accounting purposes and has the power to direct all substantive strategic and day-to-day operational decisions of the Limited Partnerships. Equity Compensation Equity compensation expense for all unit-based compensation awards is based on the grant date fair value estimated in accordance with the provisions of the Stock Compensation Topic of the FASB Accounting Standards Codification. We recognize unit-based compensation costs on a straight-line basis over the requisite service period of an award, which is generally the same as the award’s vesting term. See Note 11–Long-Term Incentive Plan, for further discussion. Income Taxes We are treated as a partnership for federal and state income tax purposes, with each partner being separately taxed on its share of the Partnership’s taxable income. Accordingly, no provision for federal or state income taxes has been recorded in the Partnership’s consolidated financial statements for any period presented in the accompanying consolidated financial statements. Reclassifications Certain amounts in prior periods have been reclassified to conform to the current reporting classifications with no effect on previously reported net income, partners’ capital or cash flow information. Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02–Leases (Topic 842), which increases transparency and comparability among organizations by recognizing right-of-use (“ROU”) lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The ASU maintains a distinction between finance leases and operating leases, which is substantially similar to the classification criteria for distinguishing between capital leases and operating leases in the previous lease guidance. Retaining this distinction allows the recognition, measurement and presentation of expenses and cash flows arising from a lease to remain similar to the previous accounting treatment. A lessee is permitted to make an accounting policy election by class of underlying asset to exclude from balance sheet recognition any lease assets and lease liabilities with a term of 12 months or less, and instead to recognize lease expense on a straight-line basis over the lease term. For both financing and operating leases, the ROU asset and lease liability will be initially measured at the present value of the lease payments in the statement of financial position. For public business entities, the amendments in this update are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. In transition, lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach with the option to adopt certain practical expedients. In July 2018, the FASB issued ASU 2018-11 which provides entities with the option to initially apply the new lease standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. We have substantially completed an analysis of our leases and continue to assess the impact of Topic 842 on our internal controls over financial reporting and will adopt Topic 842 as of January 1, 2019 using the transition method that allows a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. We have elected the transition relief package of practical expedients by applying previous accounting conclusions under ASC 840 to all of our leases that existed prior to the transition date. As a result, we will not reassess whether existing or expired contracts contain leases, the lease classification for any existing or expired leases, or whether lease origination costs qualified as initial direct costs. We will not elect the practical expedient to use hindsight in determining a lease term and impairment of ROU assets at the adoption date. Additionally, we will elect the short-term practical expedient for all of our asset classes by establishing an accounting policy to exclude leases with a term of 12 months or less and will not separate lease components from non-lease components for our specified asset classes. Lastly, we will adopt the easement practical expedient which allows the Partnership to apply ASC 842 prospectively to land easements after the adoption date. Easements that existed or expired prior to the adoption date that were not previously assessed under ASC 840 will not be reassessed. Further, we have implemented a third-party supported lease accounting system to account for the identified leases and are currently in the process of performing final testing of this system. The adoption of Topic 842 will impact the Partnership’s consolidated balance sheet due to the initial recognition of ROU assets and lease liabilities. Upon adoption of Topic 842, we expect to recognize ROU assets and corresponding lease liabilities of no greater than $20 million on our consolidated balance sheet.

Cash Distributions

Cash Distributions	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Cash Distributions	CASH DISTRIBUTIONS Our partnership agreement requires that we distribute all of our available cash from operating surplus within 45 days after the end of each quarter to unitholders of record on the applicable record date, in accordance with the terms below. Allocations of Available Cash from Operating Surplus and Incentive Distribution Rights The following table illustrates the percentage allocations of available cash from operating surplus between the unitholders and our general partner based on the specified target distribution levels. The amounts set forth under “Marginal Percentage Interest in Distributions” are the percentage interests of our general partner, as holder of our Incentive Distribution Rights (“IDRs”), and the unitholders in any available cash from operating surplus we distribute up to and including the corresponding amount in the column “Total Quarterly Distribution Per Unit Target Amount.” IDRs represent the right to receive an increasing percentage, up to a maximum of 48% (which does not include the 2% general partner interest), of quarterly distributions of available cash from operating surplus after the minimum quarterly distribution and the target distribution levels described in the table below have been achieved. All of the IDRs are currently held by our general partner. Our general partner may transfer the IDRs separately from its general partner interest. The information set forth below for our general partner include its 2% general partner interest and also assumes that our general partner has contributed any additional capital necessary to maintain its 2% general partner interest, our general partner has not transferred its IDRs, and there are no arrearages on common units. In addition, the information below for common unitholders are also applicable to quarterly distribution amounts that are less than the minimum quarterly distribution. Marginal Percentage Interest in Distributions Distribution Targets Total Quarterly Distribution Per Unit Target Amount Unitholders General Partner (including IDRs) Minimum Quarterly Distribution $0.2125 98% 2% First Target Distribution Above $0.2125 up to $0.24438 98% 2% Second Target Distribution Above $0.24438 up to $0.26563 85% 15% Third Target Distribution Above $0.26563 up to $0.31875 75% 25% Thereafter Above $0.31875 50% 50% Beginning with the distribution that was approved by the Board of Directors of the Partnership’s general partner (the “Board of Directors”) for the earnings period ended March 31, 2018, each quarterly distribution thereafter has been in excess of the maximum Third Target Distribution, or $0.31875 per common unit. Cash Distributions The Board of Directors declared the following cash distributions to the Partnership’s common and subordinated (when applicable) unitholders and to the general partner for the periods presented: (in thousands, except per unit information) Quarters Ended Total Quarterly Distribution Per Unit Total Quarterly Cash Distribution Date of Distribution 2017 March 31 $ 0.2821 $ 18,842 May 15, 2017 June 30 0.2922 19,698 August 14, 2017 September 30 0.3025 20,573 November 14, 2017 December 31 0.3133 21,489 February 14, 2018 2018 March 31 $ 0.3245 $ 22,700 May 15, 2018 June 30 0.3361 24,176 August 14, 2018 September 30 0.3479 25,678 November 13, 2018 See Note 4–Net Income per Limited Partner and General Partner Interest for information regarding the conversion of subordinated units to common units on November 14, 2017. See Note 12–Subsequent Events for information regarding the distribution that was approved by the Board of Directors on January 16, 2019 with respect to the quarter ended December 31, 2018 .

Net Income Per Limited Partner

Net Income Per Limited Partner and General Partner Interest	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Net Income Per Limited Partner and General Partner Interest	NET INCOME PER LIMITED PARTNER AND GENERAL PARTNER INTEREST We allocate net income between our general partner and limited partners using the two-class method, under which we allocate net income to our limited partners, our general partner and the holders of our IDRs in accordance with the terms of our partnership agreement. We also allocate any earnings in excess of distributions to our limited partners, our general partner and the holders of the IDRs in accordance with the terms of our partnership agreement. We allocate any distributions in excess of earnings for the period to our general partner and our limited partners based on their respective proportionate ownership interests in us, after taking into account distributions to be paid with respect to the IDRs, as set forth in our partnership agreement. Conversion of Subordinated Units From its inception through September 30, 2017, the Partnership paid equal distributions on common, subordinated and general partner units, excluding payments on IDRs, which are explained in Note 3–Cash Distributions. Upon payment of the cash distribution with respect to the quarter ended September 30, 2017, the financial requirements for the conversion of all subordinated units were satisfied. As a result, on November 15, 2017, all 29,163,121 subordinated units, which were owned entirely by CNX Resources and Noble Energy, converted into common units on a one-for-one basis. The conversion did not impact the amount of the cash distribution paid or the total number of the Partnership’s outstanding units representing limited partner interests. Historical Earnings per Unit The Partnership calculates historical earnings per unit under the two-class method and allocates the earnings or losses of a transferred business before the date of a dropdown transaction entirely to the general partner. If applicable, the previously reported earnings per unit of the limited partners would not change as a result of a dropdown transaction. 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 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 calculated by applying the treasury stock method. There were 734 and 45,066 phantom units that were not included in the calculation for the years ended December 31, 2018 and 2017 because the effect would have been antidilutive. Basic and diluted net income per limited partner unit for common and subordinated units are as follows for the periods presented (all amounts in thousands, except per unit information) : December 31, 2018 2017 2016 Net Income Attributable to General and Limited Partner Ownership Interest in CNX Midstream Partners LP $ 134,042 $ 114,993 $ 96,486 Less: General partner interest in net income, including incentive distribution rights 13,387 5,614 2,526 Limited partner interest in net income $ 120,655 $ 109,379 $ 93,960 Net income allocable to common units - Basic and Diluted $ 120,655 $ 70,837 $ 47,935 Net income allocable to subordinated units - Basic and Diluted — 38,542 46,025 Limited partner interest in net income - Basic and Diluted $ 120,655 $ 109,379 $ 93,960 Weighted average limited partner units outstanding — Basic Common units 63,635 41,710 30,044 Subordinated units — 21,872 29,163 Total 63,635 63,582 59,207 Weighted average limited partner units outstanding — Diluted Common units 63,694 41,762 30,126 Subordinated units — 21,872 29,163 Total 63,694 63,634 59,289 Net income per limited partner unit — Basic Common units $ 1.90 $ 1.70 $ 1.60 Subordinated units — 1.76 1.58 Total $ 1.90 $ 1.72 $ 1.59 Net income per limited partner unit — Diluted Common units $ 1.89 $ 1.70 $ 1.59 Subordinated units — 1.76 1.58 Total $ 1.89 $ 1.72 $ 1.58

Related Party Transaction

Related Party Transaction	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transaction	RELATED PARTY TRANSACTIONS In the ordinary course of business, we engage in related party transactions with CNX Resources (and certain of its subsidiaries) and CNX Gathering, which include the fees we charge and revenues we receive under a fixed fee gathering agreement (including electrically-powered compression CNX Resources reimburses to us) and our reimbursement of certain expenses to CNX Resources under several agreements, discussed below. In addition, we may waive or modify certain terms under these arrangements in the ordinary course of business, including the provisions of the fixed fee gathering agreement, when we determine it is in the best interests of the Partnership to do so. Any such transactions are reviewed by the Board of Directors, with oversight, as our Board of Directors deems necessary, by our conflicts committee. We also engaged in related party transactions with Noble Energy during the year ended December 31, 2017, which primarily included the fees we charged and revenues we received under our fixed fee gathering agreement with Noble Energy. Related party revenues and related party expenses are presented as separate captions within our consolidated statements of operations for the years ended December 31, 2018, 2017 and 2016. During the year ended December 31, 2018, the Partnership closed on the Shirley-Penns Acquisition and on the CNX and HG Energy Transactions. See Note 1–Description of Business for additional information. During the year ended December 31, 2017, the Partnership sold property and equipment to CNX Resources with a carrying value of $17.4 million for $14.0 million in cash proceeds. The resulting loss of $3.4 million was recorded as a loss on asset sales in the accompanying consolidated statement of operations, within the Additional Systems segment. In addition, CNX Gathering contributed assets with a carrying value of $5.0 million to the Partnership’s Anchor Systems during 2017. Operating expense–related party and general and administrative expense–related party were derived from CNX Resources in the year ended December 31, 2018 and from CNX Resources and Noble Energy in the years ended December 31, 2017 and 2016 and consisted of the following: For the Years Ended December 31, (in thousands) 2018 2017 2016 Operational services–CNX Resources $ 12,739 $ 13,166 $ 12,875 Electrical compression 7,075 12,347 16,896 Total Operating Expense — Related Party $ 19,814 $ 25,513 $ 29,771 CNX Resources $ 13,867 $ 10,167 $ 9,796 Noble Energy — 583 650 Total General and Administrative Expense — Related Party $ 13,867 $ 10,750 $ 10,446 All related party receivables were due from CNX Resources at December 31, 2018 and 2017. Related party payables consisted of the following at December 31: (in thousands) 2018 2017 CNX: Expense reimbursements $ 1,143 $ 780 Capital expenditures reimbursements 182 83 General and administrative services 3,655 1,458 Due to CNX total $ 4,980 $ 2,321 Noble Energy: General and administrative services — 55 Due to Noble Energy total $ — $ 55 Total Accounts Payable — Related Party $ 4,980 $ 2,376 In addition to the aforementioned transactions, throughout the years ended December 31, 2018, 2017 and 2016, CNX Resources and Noble Energy, through their ownership of CNX Gathering in the applicable periods, also regularly reimbursed the Partnership for capital expenditures, initially funded by the Partnership, in proportion to CNX Gathering’s noncontrolling ownership interests in the Anchor, Growth and Additional Systems. We also distributed to CNX Resources and Noble Energy amounts related to their noncontrolling ownership interest, in the applicable periods, in the earnings of the Anchor, Growth and Additional Systems as well as proceeds from sales of any assets in which CNX Resources and Noble Energy had ownership interests through their membership in CNX Gathering. This activity is recorded in the caption “Distributions to general partner and noncontrolling interest holders, net” in the consolidated statements of partners’ capital and noncontrolling interest and of cash flows. Omnibus Agreement On September 30, 2014, the date of the closing of the initial public offering of our common units (our “IPO”), we entered into an omnibus agreement with CNX Resources, Noble Energy, CNX Gathering and our general partner that addresses the following matters: • our payment of an annually-determined administrative support fee (approximately $1.9 million for the year ended December 31, 2018) for the provision of certain services by CNX Resources and its affiliates, including executive costs; • our obligation to reimburse CNX Resources and Noble Energy for all other direct or allocated costs and expenses incurred by CNX Resources and Noble Energy (through the date of the Noble Energy Asset Sale) in providing general and administrative services (which reimbursement is in addition to certain expenses of our general partner and its affiliates that are reimbursed under our partnership agreement); • our right of first offer to acquire (i) CNX Gathering’s retained interests in each of our Anchor Systems, Growth Systems and Additional Systems, (ii) CNX Gathering’s other ancillary midstream assets and (iii) any additional midstream assets that CNX Gathering develops; and • an indemnity from CNX Gathering for liabilities associated with the use, ownership or operation of our assets, including environmental liabilities, to the extent relating to the period of time prior to the closing of the IPO; and our obligation to indemnify CNX Gathering for events and conditions associated with the use, ownership or operation of our assets that occur after the closing of the IPO, including environmental liabilities. The omnibus agreement will remain in full force and effect throughout the period in which CNX Gathering controls our general partner. If CNX Gathering ceases to control our general partner, either party may terminate the omnibus agreement, provided that the indemnification obligations will remain in full force and effect in accordance with their terms. Operational Services Agreement Upon closing of our IPO, we entered into an operational services agreement with CNX Resources. On December 1, 2016, in connection with a transaction under which CNX Resources and Noble Energy separated their Marcellus Shale area of mutual interest into two separate operating areas, the operational services agreement was amended and restated. Under the amended and restated operational services agreement, CNX Resources continues to provide certain operational services to us in support of our gathering pipelines and dehydration, treating and compressor stations and facilities, including routine and emergency maintenance and repair services, routine operational activities, routine administrative services, construction and related services and such other services as we and CNX Resources may mutually agree upon from time to time. CNX Resources prepares and submits for our approval a maintenance, operating and capital budget on an annual basis. CNX Resources submits actual expenditures for reimbursement on a monthly basis, and we reimburse CNX Resources for any direct third-party costs incurred by CNX Resources in providing these services. The amended and restated operational services agreement has an initial term ending September 30, 2034 and will continue in full force and effect unless terminated by either party at the end of the initial term or any time thereafter by giving not less than six months’ prior notice to the other party of such termination. CNX Resources may terminate the operational services agreement if (1) we become insolvent, declare bankruptcy or take any action in furtherance of, or indicating our consent to, approval of, or acquiescence in, a similar proceeding or (2) upon not less than 180 days notice. We may immediately terminate the agreement (1) if CNX Resources becomes insolvent, declares bankruptcy or takes any action in furtherance of, or indicating its consent to, approval of, or acquiescence in, a similar proceeding, (2) upon a finding of CNX Resources’ willful misconduct or gross negligence that has had a material adverse effect on any of our gathering pipelines and dehydration, treating and compressor stations and facilities or our business or (3) CNX Resources is in material breach of the operational services agreement and fails to cure such default within 45 days. Under the amended and restated operational services agreement, CNX Resources will indemnify us from any claims, losses or liabilities incurred by us, including third-party claims, arising from CNX Resources’ performance of the agreement to the extent caused by CNX Resources’ gross negligence or willful misconduct. We will indemnify CNX Resources from any claims, losses or liabilities incurred by CNX Resources, including any third-party claims, arising from CNX Resources’ performance of the agreement, except to the extent such claims, losses or liabilities are caused by CNX Resources’ gross negligence or willful misconduct. Our Gathering Agreements 2018 Gathering Agreements and Amendments On January 3, 2018, we entered into the Second Amended and Restated Gas Gathering Agreement (“GGA”), which is a 20 -year, fixed-fee gathering agreement with CNX Gas that amended and restated the previous gathering agreement with CNX Gas in its entirety. The amendment did not change the fees for services we provide in the Marcellus Shale for existing wells that were covered under the prior agreement (discussed below); however, the new gas gathering agreement with CNX Gas also dedicated additional acres in the Utica Shale in and around the McQuay and Wadestown areas and introduced the following gas gathering and compression rates for the year ended December 31, 2018: • Gas Gathering: ◦ McQuay area Utica Shale - a fee of $0.225 per MMBtu; and ◦ Wadestown Marcellus Shale and Utica Shale - a fee of $0.35 per MMBtu. • Compression: ◦ For areas not benefitting from system expansion pursuant to the Second Amended and Restated GGA, compression services are included in the base fees; and ◦ In the McQuay and Wadestown areas, for wells turned in line beginning January 1, 2018 and beyond, we will receive additional fees of $0.065 per MMBtu for Tier 1 pressure services (maximum receipt point of pressure of 600 psi) and $0.130 per MMBtu for Tier 2 pressure services (maximum receipt point of pressure of 300 psi). The Second Amended and Restated GGA also committed CNX Gas to drill and complete the following numbers of wells in the McQuay area within Anchor Systems in the periods indicated, provided that if 125 wells have been drilled and completed in the Marcellus Shale, then the remainder of such planned wells must be drilled in the Utica Shale. To the extent the requisite number of wells are not drilled and completed by CNX Gas in a given period, we will be entitled to a deficiency payment per shortfall well as set out in the parenthetical below: • January 1, 2018 to December 31, 2018 - 30 wells (deficiency payment of $3.5 million per well) • January 1, 2019 to April 30, 2020 - 40 wells (deficiency payment of $3.5 million per well) • May 1, 2020 to April 30, 2021 - 40 wells (deficiency payment of $2.0 million per well) • May 1, 2021 to April 30, 2022 - 30 wells (deficiency payment of $2.0 million per well) In the event that CNX Gas drills wells and completes a number of wells in excess of the number of wells required to be drilled and completed in such period, (i) the number of excess wells drilled and completed during such period will be applied to the minimum well requirement in the succeeding period or (ii) to the extent CNX Gas was required to make deficiency payments for shortfalls in the preceding period, CNX Gas may elect to cause the Partnership to pay a refund in an amount equal to (x) the number of excess wells drilled and completed during the period, multiplied by (y) the deficiency payment paid per well during the period in which the shortfall occurred. CNX Gas satisfied its minimum well obligation for the year ended December 31, 2018. On March 16, 2018, in connection with the Shirley-Penns Acquisition, we amended the Second Amended and Restated GGA to add an MVC on volumes associated with the Shirley-Penns System through December 31, 2031. The MVC commits CNX Gas to pay the Partnership the wet gas fee under the GGA for all natural gas we gather up to a specified amount per day through December 31, 2031. We expect to recognize minimum revenues throughout the term of the MVC as follows: (in millions) Minimum Revenue Year ending December 31, 2019 $ 21.4 Year ending December 31, 2020 34.7 Year ending December 31, 2021 40.8 Year ending December 31, 2022 47.8 Year ending December 31, 2023 42.9 Remainder of term 213.7 Total revenue to be recognized under Shirley-Penns contract through December 31, 2031 $ 401.3 For all natural gas the Partnership gathers in excess of the MVC, the Partnership received a fee of $0.35 per MMBtu throughout the year ended December 31, 2018, which will escalate by 2.5% annually beginning on January 1, 2019. On May 2, 2018, we completed the CNX Transactions, pursuant to which we amended the Second Amended and Restated GGA. The amended agreement commits CNX Gas to drill and complete an additional 40 wells in the Majorsville/Mamont area within the Anchor Systems through 2023. To the extent the requisite number of wells are not drilled and completed by CNX Gas in a given period, we will be entitled to a deficiency payment per shortfall well as set out in the parenthetical below: • July 1, 2018 to December 31, 2020 - 15 wells (deficiency payment of $2.8 million per well) • January 1, 2021 - December 31, 2023 - 25 wells (deficiency payment of $2.8 million per well) Gathering Agreements Prior to 2018 On December 1, 2016, we entered into a new fixed-fee gathering agreement with CNX Gas that replaced the gathering agreement that had been in place since our IPO. Under our gathering agreement with CNX Gas, during the year ended December 31, 2018, we received a fee based on the type and scope of the midstream services we provided, summarized as follows: • With respect to natural gas from the Marcellus Shale formation that did not require downstream processing, or dry gas, we received a fee of $0.431 per MMBtu. • With respect to the natural gas that required downstream processing, or wet gas, we received: ◦ a fee of $0.296 per MMBtu in the Pittsburgh International Airport area; and ◦ a fee of $0.593 per MMBtu for all other areas in the dedication area. • With respect to natural gas from the Utica Shale formation, we received a weighted average rate of $0.15 per MMBtu. • Our fees for condensate services were $5.38 per Bbl in the Majorsville area and in the Shirley-Penns area. Each of the foregoing fees escalates by 2.5% annually, through and including the final calendar year of the initial term. Commencing on January 1, 2035, and on each January 1 thereafter, each of the applicable fees will be adjusted pursuant to the percentage change in CPI-U, but such fees will never escalate or decrease by more than 3% . For additional information related to our gas gathering agreements with CNX Gas and HG Energy, and amendments thereto, see Part I. Item 1. Business—“Our Gathering Agreements with CNX Gas and HG Energy” and Item 1A. Risk Factors—Risks Related to Our Business—“Our gathering agreements with our customers provide for the release of dedicated acreage or fee credits in certain situations.” Upon completion of its 20 -year term in 2037, our gathering agreement with CNX Gas will continue in effect from year to year until such time as the agreement is terminated by either us or CNX Gas on or before 180 days prior written notice. Registration Rights Agreement On January 3, 2018, in connection with the closing of the General Partner Transaction, the Partnership entered into a Registration Rights Agreement (the “Registration Rights Agreement”) with Noble Energy relating to the registered resale of common units that Noble Energy acquired in connection with the IPO and upon conversion of subordinated units representing limited partner interests in the Partnership (collectively, the “Registrable Securities”). Pursuant to the Registration Rights Agreement, the Partnership filed a registration statement for the registered resale of the Registrable Securities. Under the terms of the Registration Rights Agreement, Noble Energy executed an underwritten public offering of 7,475,000 of its common units in the Partnership on June 29, 2018. On September 26, 2018, Noble Energy executed private securities sales agreements with multiple buyers for the remaining 14,217,198 Retained Units, representing all of its remaining ownership of the Partnership. See Note 1–Description of Business for additional information.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	PROPERTY AND EQUIPMENT Property and equipment consisted of the following at December 31: (in thousands) 2018 2017 Estimated Useful Lives in Years Land $ 67,624 $ 76,130 N/A Gathering equipment 605,722 662,595 25 — 40 Compression equipment 199,728 180,038 30 — 40 Processing equipment 30,979 30,979 40 Assets under construction 70,341 23,099 N/A Total Property and Equipment $ 974,394 $ 972,841 Less: Accumulated Depreciation Gathering equipment $ 58,561 $ 53,544 Compression equipment 18,099 14,886 Processing equipment 5,959 5,133 Total Accumulated Depreciation $ 82,619 $ 73,563 Property and Equipment, Net $ 891,775 $ 899,278 The Partnership capitalized approximately $1.1 million of interest on assets under construction during the year ended December 31, 2018. No interest was capitalized in the year ended December 31, 2017.

Revolving Credit Facility

Revolving Credit Facility	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Revolving Credit Facility	REVOLVING CREDIT FACILITY On March 8, 2018, we entered into a $600.0 million secured revolving credit facility with an accordion feature that allows, subject to certain terms and conditions, the Partnership to increase the available borrowings under the facility by up to an additional $250.0 million . The new revolving credit facility, which includes the ability to issue letters of credit up to $100.0 million in the aggregate, replaced the prior $250.0 million unsecured revolving credit facility and matures on March 8, 2023 . The available borrowing capacity under the revolving credit facility is limited by certain financial covenants pertaining to leverage and interest coverage ratios as defined in the revolving credit facility agreement. Borrowings under our revolving credit facility bear interest at our option at either: • the base rate, which is the highest of (i) the federal funds open rate plus 0.50% ; (ii) PNC Bank, N.A.’s prime rate; or (iii) the one-month LIBOR rate plus 1.00% , in each case, plus a margin ranging from 0.75% to 1.75% ; or • the LIBOR rate, which is the LIBOR rate plus a margin ranging from 1.75% to 2.75% . We incurred a total of $ 2.4 million in interest expense related to both revolving credit facilities (not including amortization of revolver fees) during the year ended December 31, 2018. Interest on base rate loans is payable on the first business day of each calendar quarter. Interest on LIBOR loans is payable on the last day of each interest period or, in the case of interest periods longer than three months, every three months. The unused portion of our revolving credit facility is subject to a commitment fee ranging from 0.375% to 0.500% per annum depending on our most recent consolidated leverage ratio. The facility contains a number of affirmative and negative covenants that include, among others, covenants that, except in certain circumstances, restrict the ability of the Partnership, its subsidiary guarantors and certain of its non-guarantor, non-wholly-owned subsidiaries, except in certain circumstances, to: (i) create, incur, assume or suffer to exist indebtedness; (ii) create or permit to exist liens on their properties; (iii) prepay certain indebtedness unless there is no default or event of default under the facility; (iv) make or pay any dividends or distributions in excess of certain amounts; (v) merge with or into another person, liquidate or dissolve; or acquire all or substantially all of the assets of any going concern or going line of business or acquire all or a substantial portion of another person’s assets; (vi) make particular investments and loans; (vii) sell, transfer, convey, assign or dispose of its assets or properties other than in the ordinary course of business and other select instances; (viii) deal with any affiliate except in the ordinary course of business on terms no less favorable to the Partnership than it would otherwise receive in an arm’s length transaction; and (ix) amend in any material manner its certificate of incorporation, bylaws, or other organizational documents without giving prior notice to the lenders and, in some cases, obtaining the consent of the lenders. The agreement also contains customary events of default, including, but not limited to, a cross-default to certain other debt, breaches of representations and warranties, change of control events and breaches of covenants. The obligations under the revolving credit facility agreement are secured by the Partnership’s economic interests in each of the Limited Partnerships and all of the assets of the Anchor Systems. In addition, the Partnership is required to maintain at the end of each fiscal quarter: • a maximum total leverage ratio of no greater than 4.75 to 1.00 when less than $150.0 million aggregate unsecured notes are outstanding ranging to no greater than 5.50 to 1.00 in certain circumstances; • a maximum secured leverage ratio of no greater than 3.50 to 1.00; and • a minimum interest coverage ratio of no less than 2.50 to 1.00. The Partnership is in compliance with each of the aforementioned financial covenants at December 31, 2018. On December 31, 2018, the Partnership’s balance on the revolving credit facility was $ 84.0 million at an interest rate of 4.21% . After giving effect to the limitations on available capacity described in the revolving credit facility agreement, we estimate that the Partnership had approximately $ 480.0 million available for borrowing at December 31, 2018. At December 31, 2017, the outstanding balance on the then-effective revolving credit facility was $149.5 million at an interest rate of 3.11% . LONG-TERM DEBT On March 16, 2018, the Partnership, together with its wholly owned subsidiary CNX Midstream Finance Corp (“Finance Corp”), (collectively, the “Issuers”), completed a private offering of $400.0 million in 6.5% senior notes due 2026 (the “Senior Notes”), with related guarantees (the “Guarantees”) and received net proceeds of approximately $393.0 million , after deducting the initial purchasers’ discount and commissions and estimated offering expenses, which are recorded in our consolidated balance sheet as a reduction to the principal amount. Proceeds from the Senior Notes offering were primarily used to fund the Shirley-Penns Acquisition and repay existing indebtedness under our prior $250.0 million unsecured revolving credit facility. The Senior Notes mature on March 15, 2026 and accrue interest at a rate of 6.5% per year, which is payable semi-annually in arrears on March 15 and September 15. There are no principal payment requirements on the Senior Notes prior to maturity. The Senior Notes and Guarantees were issued pursuant to an indenture (the “Indenture”), dated March 16, 2018, among the Partnership, Finance Corp, the guarantors party thereto (the “Guarantors”) and UMB Bank, N.A., as trustee (the “Trustee”). The Senior Notes rank equally in right of payment with all of the Issuers’ existing and future senior indebtedness and senior to any subordinated indebtedness that the Issuers’ may incur. The Guarantees rank equally in right of payment to all of the Guarantors’ existing and future senior indebtedness. The Issuers may redeem all or part of the Senior Notes at redemption prices ranging from 104.875% beginning March 15, 2021 to 100.0% beginning March 15, 2024. Prior to March 15, 2021, the Issuers may on one or more occasions redeem up to 35.0% of the principal amount of the Senior Notes with an amount of cash not greater than the amount of the net cash proceeds from one or more equity offerings at a redemption price of 106.50% . At any time or from time to time prior to March 15, 2021, the Issuers may also redeem all or a part of the Senior Notes, at a redemption price equal to 100.0% of the principal amount thereof plus the Applicable Premium, as defined in the Indenture, plus accrued and unpaid interest. If the Partnership experiences certain kinds of changes of control, holders of the Senior Notes will be entitled to require the Partnership to repurchase all or any part of that holder’s Senior Notes pursuant to an offer on the terms set forth in the Indenture. The Partnership will offer to make a cash payment equal to 101.0% of the aggregate principal amount of the Senior Notes repurchased plus accrued and unpaid interest on the Senior Notes repurchased to, but not including, the date of purchase, subject to the rights of holders of the Senior Notes on the relevant record date to receive interest due on the relevant interest payment date. The Partnership’s long-term debt consisted of the following as of December 31, 2018 : (in thousands) Balance Senior Notes due March 2026 at 6.5% $ 400,000 Less: Unamortized debt issuance costs 1,410 Less: Unamortized bond discount 5,375 Total Long-Term Debt $ 393,215

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	REVOLVING CREDIT FACILITY On March 8, 2018, we entered into a $600.0 million secured revolving credit facility with an accordion feature that allows, subject to certain terms and conditions, the Partnership to increase the available borrowings under the facility by up to an additional $250.0 million . The new revolving credit facility, which includes the ability to issue letters of credit up to $100.0 million in the aggregate, replaced the prior $250.0 million unsecured revolving credit facility and matures on March 8, 2023 . The available borrowing capacity under the revolving credit facility is limited by certain financial covenants pertaining to leverage and interest coverage ratios as defined in the revolving credit facility agreement. Borrowings under our revolving credit facility bear interest at our option at either: • the base rate, which is the highest of (i) the federal funds open rate plus 0.50% ; (ii) PNC Bank, N.A.’s prime rate; or (iii) the one-month LIBOR rate plus 1.00% , in each case, plus a margin ranging from 0.75% to 1.75% ; or • the LIBOR rate, which is the LIBOR rate plus a margin ranging from 1.75% to 2.75% . We incurred a total of $ 2.4 million in interest expense related to both revolving credit facilities (not including amortization of revolver fees) during the year ended December 31, 2018. Interest on base rate loans is payable on the first business day of each calendar quarter. Interest on LIBOR loans is payable on the last day of each interest period or, in the case of interest periods longer than three months, every three months. The unused portion of our revolving credit facility is subject to a commitment fee ranging from 0.375% to 0.500% per annum depending on our most recent consolidated leverage ratio. The facility contains a number of affirmative and negative covenants that include, among others, covenants that, except in certain circumstances, restrict the ability of the Partnership, its subsidiary guarantors and certain of its non-guarantor, non-wholly-owned subsidiaries, except in certain circumstances, to: (i) create, incur, assume or suffer to exist indebtedness; (ii) create or permit to exist liens on their properties; (iii) prepay certain indebtedness unless there is no default or event of default under the facility; (iv) make or pay any dividends or distributions in excess of certain amounts; (v) merge with or into another person, liquidate or dissolve; or acquire all or substantially all of the assets of any going concern or going line of business or acquire all or a substantial portion of another person’s assets; (vi) make particular investments and loans; (vii) sell, transfer, convey, assign or dispose of its assets or properties other than in the ordinary course of business and other select instances; (viii) deal with any affiliate except in the ordinary course of business on terms no less favorable to the Partnership than it would otherwise receive in an arm’s length transaction; and (ix) amend in any material manner its certificate of incorporation, bylaws, or other organizational documents without giving prior notice to the lenders and, in some cases, obtaining the consent of the lenders. The agreement also contains customary events of default, including, but not limited to, a cross-default to certain other debt, breaches of representations and warranties, change of control events and breaches of covenants. The obligations under the revolving credit facility agreement are secured by the Partnership’s economic interests in each of the Limited Partnerships and all of the assets of the Anchor Systems. In addition, the Partnership is required to maintain at the end of each fiscal quarter: • a maximum total leverage ratio of no greater than 4.75 to 1.00 when less than $150.0 million aggregate unsecured notes are outstanding ranging to no greater than 5.50 to 1.00 in certain circumstances; • a maximum secured leverage ratio of no greater than 3.50 to 1.00; and • a minimum interest coverage ratio of no less than 2.50 to 1.00. The Partnership is in compliance with each of the aforementioned financial covenants at December 31, 2018. On December 31, 2018, the Partnership’s balance on the revolving credit facility was $ 84.0 million at an interest rate of 4.21% . After giving effect to the limitations on available capacity described in the revolving credit facility agreement, we estimate that the Partnership had approximately $ 480.0 million available for borrowing at December 31, 2018. At December 31, 2017, the outstanding balance on the then-effective revolving credit facility was $149.5 million at an interest rate of 3.11% . LONG-TERM DEBT On March 16, 2018, the Partnership, together with its wholly owned subsidiary CNX Midstream Finance Corp (“Finance Corp”), (collectively, the “Issuers”), completed a private offering of $400.0 million in 6.5% senior notes due 2026 (the “Senior Notes”), with related guarantees (the “Guarantees”) and received net proceeds of approximately $393.0 million , after deducting the initial purchasers’ discount and commissions and estimated offering expenses, which are recorded in our consolidated balance sheet as a reduction to the principal amount. Proceeds from the Senior Notes offering were primarily used to fund the Shirley-Penns Acquisition and repay existing indebtedness under our prior $250.0 million unsecured revolving credit facility. The Senior Notes mature on March 15, 2026 and accrue interest at a rate of 6.5% per year, which is payable semi-annually in arrears on March 15 and September 15. There are no principal payment requirements on the Senior Notes prior to maturity. The Senior Notes and Guarantees were issued pursuant to an indenture (the “Indenture”), dated March 16, 2018, among the Partnership, Finance Corp, the guarantors party thereto (the “Guarantors”) and UMB Bank, N.A., as trustee (the “Trustee”). The Senior Notes rank equally in right of payment with all of the Issuers’ existing and future senior indebtedness and senior to any subordinated indebtedness that the Issuers’ may incur. The Guarantees rank equally in right of payment to all of the Guarantors’ existing and future senior indebtedness. The Issuers may redeem all or part of the Senior Notes at redemption prices ranging from 104.875% beginning March 15, 2021 to 100.0% beginning March 15, 2024. Prior to March 15, 2021, the Issuers may on one or more occasions redeem up to 35.0% of the principal amount of the Senior Notes with an amount of cash not greater than the amount of the net cash proceeds from one or more equity offerings at a redemption price of 106.50% . At any time or from time to time prior to March 15, 2021, the Issuers may also redeem all or a part of the Senior Notes, at a redemption price equal to 100.0% of the principal amount thereof plus the Applicable Premium, as defined in the Indenture, plus accrued and unpaid interest. If the Partnership experiences certain kinds of changes of control, holders of the Senior Notes will be entitled to require the Partnership to repurchase all or any part of that holder’s Senior Notes pursuant to an offer on the terms set forth in the Indenture. The Partnership will offer to make a cash payment equal to 101.0% of the aggregate principal amount of the Senior Notes repurchased plus accrued and unpaid interest on the Senior Notes repurchased to, but not including, the date of purchase, subject to the rights of holders of the Senior Notes on the relevant record date to receive interest due on the relevant interest payment date. The Partnership’s long-term debt consisted of the following as of December 31, 2018 : (in thousands) Balance Senior Notes due March 2026 at 6.5% $ 400,000 Less: Unamortized debt issuance costs 1,410 Less: Unamortized bond discount 5,375 Total Long-Term Debt $ 393,215

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Leases We have entered into various non-cancelable operating leases, primarily related to compression facilities. Future minimum lease payments under operating leases as of December 31, 2018 are as follows: (in thousands) Minimum Lease Payments For the year ending December 31, 2019 $ 6,637 For the year ending December 31, 2020 4,755 $ 11,392 Rental expense under operating leases was $7.9 million, $7.6 million and $7.7 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively. These expenses are included within operating expense–third party on our consolidated statement of operations. Litigation The Partnership may become involved in certain legal proceedings from time to time, and where appropriate, we have accrued our estimate of the probable costs for the resolution of these claims. The Partnership believes that the ultimate outcome of any matter currently pending against the Partnership will not materially affect the Partnership’s business, financial condition, results of operations, liquidity or ability to make distributions.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION Operating segments are the revenue-producing components of a company for which separate financial information is produced internally and is subject to evaluation by the chief operating decision maker in deciding how to allocate resources. Prior to the CNX and HG Energy Transactions, the Partnership had three operating segments, which also represented its reportable segments - the Anchor Systems, Growth Systems and Additional Systems, each of which does business entirely within the United States of America. See Note 1–Description of Business for additional information. During the first quarter of 2018, the Partnership, through its 100% interest in the Anchor Systems, completed the Shirley-Penns Acquisition. Prior to March 16, 2018, the Partnership held a 5% controlling interest in the earnings and throughput related to the Shirley-Penns System; accordingly, until March 16, 2018, results attributable to limited and general partners of the Partnership reflect a 5% interest in the Shirley-Penns System. Results net to the Partnership include activity related to the Shirley-Penns Acquisition beginning March 16, 2018. However, in accordance with ASC 280 - Segment Reporting, information is reported in the tables below, for comparability purposes, as if the Shirley-Penns Acquisition occurred on January 1, 2016. In connection with the CNX and HG Energy Transactions, the Partnership distributed its 5% interest in the Growth Systems and related assets as well as its 5% interest in the Moundsville area midstream assets, which were previously a part of the Additional Systems, to CNX Gathering, which transferred these assets to HG Energy. Because the transferred assets had activity for the years ended December 31, 2017 and 2016 and for the period January 1, 2018 through May 2, 2018, we will continue to present consistent segment information with regards to this transaction for comparative purposes. Segment results for the periods presented were as follows: For the Years Ended December 31, (in thousands) 2018 2017 2016 Gathering Revenue: Anchor Systems $ 240,445 $ 209,470 $ 215,492 Growth Systems 2,572 8,152 10,359 Additional Systems 13,651 16,226 13,360 Total Gathering Revenue $ 256,668 $ 233,848 $ 239,211 Net Income (Loss): Anchor Systems $ 139,386 $ 129,486 $ 132,221 Growth Systems 379 607 (6,624 ) Additional Systems (770 ) 3,969 4,525 Total Net Income $ 138,995 $ 134,062 $ 130,122 Depreciation Expense: Anchor Systems $ 19,009 $ 17,008 $ 16,132 Growth Systems 748 2,193 2,157 Additional Systems 2,182 3,491 2,912 Total Depreciation Expense $ 21,939 $ 22,692 $ 21,201 Capital Expenditures for Segment Assets: Anchor Systems $ 136,615 $ 46,393 $ 41,451 Growth Systems 120 702 1,089 Additional Systems 8,596 1,271 8,120 Total Capital Expenditures $ 145,331 $ 48,366 $ 50,660 Segment assets as of the dates presented are as follows: December 31, (in thousands) 2018 2017 Segment Assets: Anchor Systems $ 832,885 $ 694,942 Growth Systems — 92,659 Additional Systems 92,543 138,988 Total Segment Assets $ 925,428 $ 926,589

Long-Term Incentive Plan

Long-Term Incentive Plan	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Long-Term Incentive Plan	LONG-TERM INCENTIVE PLAN Under the Partnership’s 2014 Long-Term Incentive Plan (our “LTIP”), our general partner may issue long-term equity-based awards to directors, officers and employees of the general partner or its affiliates, or to any consultants, affiliates of our general partner or other individuals who perform services on behalf of the Partnership. The Partnership is responsible for the cost of awards granted under the LTIP, which limits the number of units that may be delivered pursuant to vested awards to 5,800,000 common units, subject to proportionate adjustment in the event of unit splits and similar events. Common units subject to awards that are canceled, forfeited, withheld to satisfy tax withholding obligations or otherwise terminated without delivery of the common units will be available for delivery pursuant to other awards. The following table presents phantom unit activity during the year ended December 31, 2018: Number of Units Weighted Average Grant Date Fair Value Total awarded and unvested at December 31, 2017 134,153 $ 16.40 Granted 139,234 19.14 Vested (72,469) 16.64 Forfeited (22,289) 16.59 Total awarded and unvested at December 31, 2018 178,629 $ 18.35 The Partnership accounts for phantom units as equity awards and records compensation expense on a straight line basis over the vesting period based on the fair value of the awards on their grant dates. Awards granted to independent directors vest over a period of one year, and awards granted to certain officers and employees of the general partner vest 33% per year over a period of three years. The Partnership recognized $2.4 million , $1.2 million , and $0.8 million of compensation expense for the years ended December 31, 2018 , 2017 and 2016 , respectively, which was included in general and administrative expense–related party in the consolidated statements of operations. At December 31, 2018 , unrecognized compensation expense related to all outstanding awards was $1.3 million , which is expected to be recognized over the following two years .

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS On January 16, 2019 , the board of directors of our general partner declared a cash distribution to the Partnership’s unitholders for the fourth quarter of 2018 of $0.3603 per common unit. The cash distribution will be paid on February 13, 2019 to unitholders of record as of the close of business on February 5, 2019 .

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	The accompanying audited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”).
Use of Estimates	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and various disclosures. Actual results could differ from those estimates, which are evaluated on an ongoing basis, utilizing historical experience and other methods considered reasonable under the particular circumstances. Although these estimates are based on management’s best available knowledge at the time, changes in facts and circumstances or discovery of new facts or circumstances may result in revised estimates and actual results may differ from these estimates. Effects on the Partnership’s business, financial position and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revision become known.
Principles of Consolidation	The consolidated financial statements include the accounts of the Partnership and all of its controlled subsidiaries, including 100% of each of the Anchor Systems, Growth Systems and Additional Systems in the relevant periods. Although the Partnership has less than a 100% economic interest in the Growth and Additional Systems, each were consolidated fully with the results of the Partnership. However, after adjusting for noncontrolling interests, net income attributable to general and limited partner ownership interests in the Partnership reflect only that portion of net income that is attributable to the Partnership’s unitholders. For example, as a result of the Anchor Systems Acquisition, net income attributable to general and limited partner ownership interests in the Partnership includes 100% of the results of the Anchor Systems for the period subsequent to the closing date of that transaction. In addition, net income attributable to general and limited partner ownership interests in the Partnership includes 100% of the results of the Shirley-Penns Systems for the period subsequent to the closing date of that transaction. Transactions between the Partnership, CNX and Noble Energy have been identified in the consolidated financial statements as transactions between related parties in the relevant periods and are discussed in Note 5–Related Party Transactions.
Revenue Recognition	On January 1, 2018, the Partnership adopted Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers and all the related amendments (“new revenue standard”) using the modified retrospective method. We did not have a transition adjustment as a result of the adoption of the new revenue standard. Revenues from contracts with customers We record revenue when obligations under the terms of the contracts with our shippers are satisfied; generally this occurs on a daily basis as we gather gas at the wellhead. Revenue is measured as the amount of consideration we expect to receive in exchange for providing the natural gas gathering services. Nature of performance obligations At contract inception, we assess the services promised in our contracts with customers and identify a performance obligation for each promised service that is distinct. To identify the performance obligations, we consider all of the services promised in the contract, regardless of whether they are explicitly stated or are implied by customary business practices. Our revenue is generated from natural gas gathering activities. The gas gathering services are interruptible in nature and include charges for the volume of gas actually gathered and do not guarantee access to the system. Volumetric-based fees relate to actual volumes gathered. In general, the interruptible gathering of each unit (MMBtu) of natural gas represents a separate performance obligation. Payment terms for these contracts require payment within 25 days of the end of the calendar month in which the hydrocarbons are gathered. Transaction price allocated to remaining performance obligations The new revenue standard requires that we disclose the aggregate amount of transaction price that is allocated to performance obligations that have not yet been satisfied. However, the guidance provides certain practical expedients that limit this requirement. Substantially all of our revenues are derived from contracts with CNX Resources and HG Energy that have terms of greater than one year. Under these contracts, the interruptible gathering of each unit of natural gas represents a separate performance obligation. For revenue associated with the Shirley-Penns System, for which we have a contract with remaining performance obligations, the aggregate amount of the transaction price allocated to remaining performance obligations was $401.3 million at December 31, 2018. We expect to recognize minimum revenue of $21.4 million and $34.7 million , respectively, during the years ending December 31, 2019 and December 31, 2020 under the MVC. The amount of revenue associated with this contract up to the minimum volume commitment (“MVC”) is fixed in nature, and volumes that we may gather above the MVC will be variable in nature. As of December 31, 2018, no future performance obligations exist relative to volumes to be gathered in excess of the MVC as the related volumes have not yet been nominated for gathering. Therefore, we have not disclosed the value of unsatisfied performance obligations for the variable aspect of this agreement, nor have we disclosed the value of other unsatisfied performance obligations that are variable in nature. Prior-period performance obligations We record revenue when obligations under the terms of the contracts with our shippers are satisfied; generally this occurs on a daily basis when we gather gas at the wellhead. In some cases, we are required to estimate the amount of natural gas that we have gathered during an accounting period and record any differences between our estimates and the actual units of natural gas that we gathered in the following month. We have existing internal controls for our revenue estimation process and related accruals; historically, any identified differences between our revenue estimates and actual revenue received have not been significant. For the years ended December 31, 2018 and 2017, revenue recognized in the reporting period related to performance obligations satisfied in prior reporting periods was not material. Disaggregation of revenue See Note 10–Segment Information for additional information. Contract balances We invoice customers once our performance obligations have been satisfied, at which point payment becomes unconditional. Accordingly, our contracts with customers do not give rise to contract assets or liabilities under the new revenue standard. We also have no contract assets recognized from the costs. Classification The fees we charge our affiliates, including our Sponsor, are recorded in gathering revenue — related party in our consolidated statements of operations. Related party fees also included those charged to Noble Energy through the date of the Noble Energy Asset Sale. Fees from midstream services we perform for HG Energy, and any other third party shipper, are recorded in gathering revenue — third party in our consolidated statements of operations.
Cash	Cash includes cash on hand and on deposit at banking institutions.
Receivables	Receivables are recorded at the invoiced amount and do not bear interest. When applicable, we reserve for specific accounts receivable when it is probable that all or a part of an outstanding balance will not be collected, such as customer bankruptcies. Collectability is determined based on terms of sale, credit status of customers and various other circumstances. We regularly review collectability and establish or adjust the reserve as necessary using the specific identification method. Account balances are charged off against the reserve after all means of collection have been exhausted and the potential for recovery is considered remote.
Fair Value Measurement	The Financial Accounting Standards Board (the “FASB”) Accounting Standards Codification Topic 820, Fair Value Measurements and Disclosures, clarifies the definition of fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements. This guidance also relates to all nonfinancial assets and liabilities that are not recognized or disclosed on a recurring basis (e.g., the initial recognition of asset retirement obligations and impairments of long‑lived assets). The fair value is the price that we estimate we would receive upon selling an asset or that we would pay to transfer a liability in an orderly transaction between market participants at the measurement date. A fair value hierarchy is used to prioritize input to valuation techniques used to estimate fair value. An asset or liability subject to the fair value requirements is categorized within the hierarchy based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. The highest priority (Level 1) is given to unadjusted quoted market prices in active markets for identical assets or liabilities, and the lowest priority (Level 3) is given to unobservable inputs. Level 2 inputs are data, other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly. The carrying values on our balance sheet of our current assets, current liabilities and revolving credit facility approximate fair values due to their short maturities.
Property and Equipment	Property and equipment is recorded at cost upon acquisition and is depreciated on a straight-line basis over the assets’ estimated useful lives or over their lease terms of the assets. Expenditures which extend the useful lives of existing property and equipment are capitalized. When properties are retired or otherwise disposed, the related cost and accumulated depreciation are removed from the respective accounts and any profit or loss on disposition is recognized as a gain or loss. The Partnership evaluates whether long-lived assets have been impaired and have processes in place to ensure that we become aware of such indicators. Impairment indicators include, but are not limited to, sustained decreases in commodity prices, a decline in customer well results and lower throughput forecasts, and increases in construction or operating costs. For such long-lived assets, impairment exists when the carrying amount of an asset or group of assets exceeds our estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset or group of assets. If the carrying amount of the long-lived asset(s) is not recoverable, based on the estimated future undiscounted cash flows, the impairment loss would be measured as the excess of the asset’s carrying amount over its estimated fair value. In the event that impairment indicators exist, we conduct an impairment test. Fair value represents the estimated price between market participants to sell an asset in the principal or most advantageous market for the asset, based on assumptions a market participant would make. When warranted, management assesses the fair value of long-lived assets using commonly accepted techniques and may use more than one source in making such assessments. Sources used to determine fair value include, but are not limited to, recent third-party comparable sales, internally developed discounted cash flow analyses, and analyses from outside advisors. Significant changes, such as the condition of an asset or management’s intent to utilize the asset, generally require management to reassess the cash flows related to long-lived assets.
Environmental Matters	We are subject to various federal, state and local laws and regulations relating to the protection of the environment. Environmental expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations, and do not contribute to current or future revenue generation, are expensed. Liabilities are recorded when environmental assessments and/or clean-ups are probable, and the costs can be reasonably estimated. At this time, we are unable to assess the timing and/or effect of potential liabilities related to greenhouse gas emissions or other environmental issues.
Asset Retirement Obligations	Our gathering pipelines and compressor stations have an indeterminate life. If properly maintained, they will operate for an indeterminate period as long as supply and demand for natural gas exists, which we expect for the foreseeable future. We are under no legal or contractual obligation to restore or dismantle our gathering system upon abandonment.
Variable Interest Entities	Each of the Anchor and Additional Systems, and our former Growth Systems (the “ Limited Partnerships”) is also a limited partnership and a variable interest entity ( “ VIE”). These VIEs correspond with the manner in which we report our segment information in Note 10–Segment Information, which also includes information regarding the Partnership’s involvement with each of these VIEs and their relative contributions to our financial position, operating results and cash flows. The Partnership fully consolidates each of the Limited Partnerships through its ownership of the Operating Company, which, through its general partner ownership interest in each of the Limited Partnerships, is considered to be the primary beneficiary for accounting purposes and has the power to direct all substantive strategic and day-to-day operational decisions of the Limited Partnerships.
Equity Compensation	Equity compensation expense for all unit-based compensation awards is based on the grant date fair value estimated in accordance with the provisions of the Stock Compensation Topic of the FASB Accounting Standards Codification. We recognize unit-based compensation costs on a straight-line basis over the requisite service period of an award, which is generally the same as the award’s vesting term. See Note 11–Long-Term Incentive Plan, for further discussion.
Income Taxes	We are treated as a partnership for federal and state income tax purposes, with each partner being separately taxed on its share of the Partnership’s taxable income. Accordingly, no provision for federal or state income taxes has been recorded in the Partnership’s consolidated financial statements for any period presented in the accompanying consolidated financial statements.
Recent Accounting Pronouncements	In February 2016, the FASB issued ASU 2016-02–Leases (Topic 842), which increases transparency and comparability among organizations by recognizing right-of-use (“ROU”) lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The ASU maintains a distinction between finance leases and operating leases, which is substantially similar to the classification criteria for distinguishing between capital leases and operating leases in the previous lease guidance. Retaining this distinction allows the recognition, measurement and presentation of expenses and cash flows arising from a lease to remain similar to the previous accounting treatment. A lessee is permitted to make an accounting policy election by class of underlying asset to exclude from balance sheet recognition any lease assets and lease liabilities with a term of 12 months or less, and instead to recognize lease expense on a straight-line basis over the lease term. For both financing and operating leases, the ROU asset and lease liability will be initially measured at the present value of the lease payments in the statement of financial position. For public business entities, the amendments in this update are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. In transition, lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach with the option to adopt certain practical expedients. In July 2018, the FASB issued ASU 2018-11 which provides entities with the option to initially apply the new lease standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. We have substantially completed an analysis of our leases and continue to assess the impact of Topic 842 on our internal controls over financial reporting and will adopt Topic 842 as of January 1, 2019 using the transition method that allows a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. We have elected the transition relief package of practical expedients by applying previous accounting conclusions under ASC 840 to all of our leases that existed prior to the transition date. As a result, we will not reassess whether existing or expired contracts contain leases, the lease classification for any existing or expired leases, or whether lease origination costs qualified as initial direct costs. We will not elect the practical expedient to use hindsight in determining a lease term and impairment of ROU assets at the adoption date. Additionally, we will elect the short-term practical expedient for all of our asset classes by establishing an accounting policy to exclude leases with a term of 12 months or less and will not separate lease components from non-lease components for our specified asset classes. Lastly, we will adopt the easement practical expedient which allows the Partnership to apply ASC 842 prospectively to land easements after the adoption date. Easements that existed or expired prior to the adoption date that were not previously assessed under ASC 840 will not be reassessed. Further, we have implemented a third-party supported lease accounting system to account for the identified leases and are currently in the process of performing final testing of this system. The adoption of Topic 842 will impact the Partnership’s consolidated balance sheet due to the initial recognition of ROU assets and lease liabilities. Upon adoption of Topic 842, we expect to recognize ROU assets and corresponding lease liabilities of no greater than $20 million on our consolidated balance sheet.

Cash Distributions (Tables)

Cash Distributions (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of Target Distributions	The information set forth below for our general partner include its 2% general partner interest and also assumes that our general partner has contributed any additional capital necessary to maintain its 2% general partner interest, our general partner has not transferred its IDRs, and there are no arrearages on common units. In addition, the information below for common unitholders are also applicable to quarterly distribution amounts that are less than the minimum quarterly distribution. Marginal Percentage Interest in Distributions Distribution Targets Total Quarterly Distribution Per Unit Target Amount Unitholders General Partner (including IDRs) Minimum Quarterly Distribution $0.2125 98% 2% First Target Distribution Above $0.2125 up to $0.24438 98% 2% Second Target Distribution Above $0.24438 up to $0.26563 85% 15% Third Target Distribution Above $0.26563 up to $0.31875 75% 25% Thereafter Above $0.31875 50% 50%
Cash Distributions	The Board of Directors declared the following cash distributions to the Partnership’s common and subordinated (when applicable) unitholders and to the general partner for the periods presented: (in thousands, except per unit information) Quarters Ended Total Quarterly Distribution Per Unit Total Quarterly Cash Distribution Date of Distribution 2017 March 31 $ 0.2821 $ 18,842 May 15, 2017 June 30 0.2922 19,698 August 14, 2017 September 30 0.3025 20,573 November 14, 2017 December 31 0.3133 21,489 February 14, 2018 2018 March 31 $ 0.3245 $ 22,700 May 15, 2018 June 30 0.3361 24,176 August 14, 2018 September 30 0.3479 25,678 November 13, 2018

Net Income Per Limited Partne_2

Net Income Per Limited Partner and General Partner Interest (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Net Income (Loss) Per Unit	Basic and diluted net income per limited partner unit for common and subordinated units are as follows for the periods presented (all amounts in thousands, except per unit information) : December 31, 2018 2017 2016 Net Income Attributable to General and Limited Partner Ownership Interest in CNX Midstream Partners LP $ 134,042 $ 114,993 $ 96,486 Less: General partner interest in net income, including incentive distribution rights 13,387 5,614 2,526 Limited partner interest in net income $ 120,655 $ 109,379 $ 93,960 Net income allocable to common units - Basic and Diluted $ 120,655 $ 70,837 $ 47,935 Net income allocable to subordinated units - Basic and Diluted — 38,542 46,025 Limited partner interest in net income - Basic and Diluted $ 120,655 $ 109,379 $ 93,960 Weighted average limited partner units outstanding — Basic Common units 63,635 41,710 30,044 Subordinated units — 21,872 29,163 Total 63,635 63,582 59,207 Weighted average limited partner units outstanding — Diluted Common units 63,694 41,762 30,126 Subordinated units — 21,872 29,163 Total 63,694 63,634 59,289 Net income per limited partner unit — Basic Common units $ 1.90 $ 1.70 $ 1.60 Subordinated units — 1.76 1.58 Total $ 1.90 $ 1.72 $ 1.59 Net income per limited partner unit — Diluted Common units $ 1.89 $ 1.70 $ 1.59 Subordinated units — 1.76 1.58 Total $ 1.89 $ 1.72 $ 1.58

Related Party Transaction (Tabl

Related Party Transaction (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Operating expense–related party and general and administrative expense–related party were derived from CNX Resources in the year ended December 31, 2018 and from CNX Resources and Noble Energy in the years ended December 31, 2017 and 2016 and consisted of the following: For the Years Ended December 31, (in thousands) 2018 2017 2016 Operational services–CNX Resources $ 12,739 $ 13,166 $ 12,875 Electrical compression 7,075 12,347 16,896 Total Operating Expense — Related Party $ 19,814 $ 25,513 $ 29,771 CNX Resources $ 13,867 $ 10,167 $ 9,796 Noble Energy — 583 650 Total General and Administrative Expense — Related Party $ 13,867 $ 10,750 $ 10,446
Schedule of Related Party Payables	All related party receivables were due from CNX Resources at December 31, 2018 and 2017. Related party payables consisted of the following at December 31: (in thousands) 2018 2017 CNX: Expense reimbursements $ 1,143 $ 780 Capital expenditures reimbursements 182 83 General and administrative services 3,655 1,458 Due to CNX total $ 4,980 $ 2,321 Noble Energy: General and administrative services — 55 Due to Noble Energy total $ — $ 55 Total Accounts Payable — Related Party $ 4,980 $ 2,376
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	We expect to recognize minimum revenues throughout the term of the MVC as follows: (in millions) Minimum Revenue Year ending December 31, 2019 $ 21.4 Year ending December 31, 2020 34.7 Year ending December 31, 2021 40.8 Year ending December 31, 2022 47.8 Year ending December 31, 2023 42.9 Remainder of term 213.7 Total revenue to be recognized under Shirley-Penns contract through December 31, 2031 $ 401.3

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following at December 31: (in thousands) 2018 2017 Estimated Useful Lives in Years Land $ 67,624 $ 76,130 N/A Gathering equipment 605,722 662,595 25 — 40 Compression equipment 199,728 180,038 30 — 40 Processing equipment 30,979 30,979 40 Assets under construction 70,341 23,099 N/A Total Property and Equipment $ 974,394 $ 972,841 Less: Accumulated Depreciation Gathering equipment $ 58,561 $ 53,544 Compression equipment 18,099 14,886 Processing equipment 5,959 5,133 Total Accumulated Depreciation $ 82,619 $ 73,563 Property and Equipment, Net $ 891,775 $ 899,278

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt	The Partnership’s long-term debt consisted of the following as of December 31, 2018 : (in thousands) Balance Senior Notes due March 2026 at 6.5% $ 400,000 Less: Unamortized debt issuance costs 1,410 Less: Unamortized bond discount 5,375 Total Long-Term Debt $ 393,215

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Future minimum lease payments	Future minimum lease payments under operating leases as of December 31, 2018 are as follows: (in thousands) Minimum Lease Payments For the year ending December 31, 2019 $ 6,637 For the year ending December 31, 2020 4,755 $ 11,392

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of Operating Revenues and Income from Operations	Segment results for the periods presented were as follows: For the Years Ended December 31, (in thousands) 2018 2017 2016 Gathering Revenue: Anchor Systems $ 240,445 $ 209,470 $ 215,492 Growth Systems 2,572 8,152 10,359 Additional Systems 13,651 16,226 13,360 Total Gathering Revenue $ 256,668 $ 233,848 $ 239,211 Net Income (Loss): Anchor Systems $ 139,386 $ 129,486 $ 132,221 Growth Systems 379 607 (6,624 ) Additional Systems (770 ) 3,969 4,525 Total Net Income $ 138,995 $ 134,062 $ 130,122 Depreciation Expense: Anchor Systems $ 19,009 $ 17,008 $ 16,132 Growth Systems 748 2,193 2,157 Additional Systems 2,182 3,491 2,912 Total Depreciation Expense $ 21,939 $ 22,692 $ 21,201 Capital Expenditures for Segment Assets: Anchor Systems $ 136,615 $ 46,393 $ 41,451 Growth Systems 120 702 1,089 Additional Systems 8,596 1,271 8,120 Total Capital Expenditures $ 145,331 $ 48,366 $ 50,660
Reconciliation of Assets from Segment to Consolidated	Segment assets as of the dates presented are as follows: December 31, (in thousands) 2018 2017 Segment Assets: Anchor Systems $ 832,885 $ 694,942 Growth Systems — 92,659 Additional Systems 92,543 138,988 Total Segment Assets $ 925,428 $ 926,589

Long-Term Incentive Plan (Table

Long-Term Incentive Plan (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Unvested Units Activity	The following table presents phantom unit activity during the year ended December 31, 2018: Number of Units Weighted Average Grant Date Fair Value Total awarded and unvested at December 31, 2017 134,153 $ 16.40 Granted 139,234 19.14 Vested (72,469) 16.64 Forfeited (22,289) 16.59 Total awarded and unvested at December 31, 2018 178,629 $ 18.35

Description of Business - Partn

Description of Business - Partnership Summary and Description of Business (Details) $ in Millions	Sep. 26, 2018shares	Jun. 29, 2018shares	Jan. 03, 2018USD ($)shares	Nov. 16, 2016USD ($)	Sep. 30, 2018	May 02, 2018segment	Sep. 30, 2018system	Dec. 31, 2018segment	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Number of operating segments | segment						3
Number of primary midstream systems | system							4
Anchor and Additional Systems
Schedule of Equity Method Investments [Line Items]
Number of operating segments | segment								2
Additional Systems
Schedule of Equity Method Investments [Line Items]
Ownership percentage after all transactions								5.00%
Additional Systems | CNX Gathering
Schedule of Equity Method Investments [Line Items]
Noncontrolling interest, percent								95.00%
CNX Gas | NBL Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Cash consideration transfered to purchase limited partner controlling interest | $			$ 305
Noble Energy
Schedule of Equity Method Investments [Line Items]
Units outstanding (in units) | shares			21,692,198
Sale of units (in units) | shares	14,217,198	7,475,000
Shirley-Penns System | Anchor Systems
Schedule of Equity Method Investments [Line Items]
Ownership interest					100.00%
Shirley-Penns System | Additional Systems
Schedule of Equity Method Investments [Line Items]
Ownership interest					5.00%
CNX Gathering LLC | CNX Gas
Schedule of Equity Method Investments [Line Items]
Ownership interest			100.00%
CNX Gathering LLC | CNX Gas | NBL Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Limited partner controlling interest acquired, percentage			50.00%
Anchor Systems
Schedule of Equity Method Investments [Line Items]
Limited partner controlling interest acquired, percentage				25.00%					25.00%
Cash consideration transfered to purchase limited partner controlling interest | $				$ 140
Ownership percentage after all transactions								100.00%

Description of Business - CNX R

Description of Business - CNX Resources Transactions with New Gas Gathering Agreements (Details) $ in Millions	May 03, 2018USD ($)awell	May 02, 2018well
Exchange Transaction
Schedule of Equity Method Investments [Line Items]
Distribution Of Interests, Reduction In Property And Equipment, Net | $	$ 133.4
Distribution Of Interests, Reduction In Noncontrolling Interest | $	179.5
Distribution Of Interests, Increase In Common Units | $	46.1
Exchange Transaction | CNX Gas
Schedule of Equity Method Investments [Line Items]
Related party transaction, cash contribution to be received | $	$ 2
Exchange Transaction | Anchor Systems
Schedule of Equity Method Investments [Line Items]
Acres divested	4,200
Exchange Transaction | Anchor Systems | CNX Gas
Schedule of Equity Method Investments [Line Items]
Exploratory wells committed | well	40
Exchange Transaction | Growth Systems
Schedule of Equity Method Investments [Line Items]
Noncontrolling interest, percent	5.00%
Exchange Transaction | Growth and Additional Systems
Schedule of Equity Method Investments [Line Items]
Acres divested	275,000
Exchange Transaction | Utica Shale formation | Anchor Systems | CNX Gas
Schedule of Equity Method Investments [Line Items]
Additional acres dedicated (in acres)	16,100
Exchange Transaction | Moundsville
Schedule of Equity Method Investments [Line Items]
Noncontrolling interest, percent	5.00%
Affiliated Entity
Schedule of Equity Method Investments [Line Items]
Exploratory wells committed | well	192	140
Affiliated Entity | Exchange Transaction
Schedule of Equity Method Investments [Line Items]
Acres divested	18,000
Affiliated Entity | Exchange Transaction | Anchor Systems
Schedule of Equity Method Investments [Line Items]
Exploratory wells committed | well	12
Affiliated Entity | Exchange Transaction | Growth and Additional Systems
Schedule of Equity Method Investments [Line Items]
Acres divested	14,000

Description of Business - Acqui

Description of Business - Acquisition of Shirley-Penns Systems (Details) - USD ($) $ in Millions	Mar. 16, 2018	Mar. 15, 2018	Dec. 31, 2017	Sep. 30, 2014
Additional Systems | Shirley-Penns System
Business Acquisition [Line Items]
Noncontrolling interest, percent		95.00%
Cash consideration transfered to purchase limited partner controlling interest	$ 265
Additional Systems | Devco III LP - Shirley Pennsboro
Business Acquisition [Line Items]
Noncontrolling interest, percent			95.00%
CNX Gathering LLC | Additional Systems
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by parent				5.00%
Senior Notes
Business Acquisition [Line Items]
Stated rate	6.50%

Description of Business - Acq_2

Description of Business - Acquisition of Remaining Interest in the Anchor Systems (Details) - USD ($) $ / shares in Units, $ in Millions	Nov. 16, 2016	Dec. 31, 2018	Dec. 31, 2016
Business Acquisition [Line Items]
General partner's ownership interest (as a percent)		2.00%
Anchor Systems
Business Acquisition [Line Items]
Limited partner controlling interest acquired, percentage	25.00%		25.00%
Cash consideration transfered to purchase limited partner controlling interest	$ 140
Common units issued as consideration transferred (in shares)	5,183,154
Issue price of common units issued (USD per unit)	$ 20.42
CNX Gathering LLC
Business Acquisition [Line Items]
General partner's ownership interest (as a percent)	2.00%
CNX Gas | Anchor Systems
Business Acquisition [Line Items]
Unit consideration to acquire business, percentage	50.00%
NBL Midstream, LLC | Anchor Systems
Business Acquisition [Line Items]
Unit consideration to acquire business, percentage	50.00%

Significant Accounting Polici_3

Significant Accounting Policies - Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2019
Accounting Policies [Abstract]
Revenue, payment terms	25 days
Timing of satisfaction of performance obligation and payment		Substantially all of our revenues are derived from contracts with CNX Resources and HG Energy that have terms of greater than one year.
Allowance for doubtful accounts receivable		$ 0	$ 0
Fair Value of long-term debt		380,000,000
Tangible asset impairments		0	0	$ 0
Asset retirement obligation		$ 0	$ 0
Accounting Standards Update 2016-02 | Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right of use					$ 20,000,000
Operating lease liability					$ 20,000,000

Significant Accounting Polici_4

Significant Accounting Policies - Revenue, Remaining Performance Obligation (Details) $ in Millions	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 21.4
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 34.7
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 40.8
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 47.8
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 42.9
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 401.3
Performance obligations expected to be satisfied, expected timing

Cash Distributions - Narrative

Cash Distributions - Narrative (Details)	12 Months Ended
	Dec. 31, 2018$ / shares
Distribution Made to Limited Partner [Line Items]
Period to distribute available cash (in days)	45 days
General partner's ownership interest (as a percent)	2.00%
Maximum
Distribution Made to Limited Partner [Line Items]
Incentive distribution, rate (as a percent)	48.00%
Third Target Distribution | Maximum
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	$ 0.31875

Cash Distributions - Allocation

Cash Distributions - Allocations of Available Cash from Operating Surplus and Incentive Distribution Rights (Details)	12 Months Ended
	Dec. 31, 2018$ / shares
Minimum Quarterly Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	$ 0.2125
Marginal percentage interest in distributions, unitholders (as a percent)	98.00%
Marginal percentage interest in distributions, general partner (as a percent)	2.00%
First Target Distribution
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions, unitholders (as a percent)	98.00%
Marginal percentage interest in distributions, general partner (as a percent)	2.00%
Second Target Distribution
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions, unitholders (as a percent)	85.00%
Marginal percentage interest in distributions, general partner (as a percent)	15.00%
Third Target Distribution
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions, unitholders (as a percent)	75.00%
Marginal percentage interest in distributions, general partner (as a percent)	25.00%
Thereafter Distributions
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions, unitholders (as a percent)	50.00%
Marginal percentage interest in distributions, general partner (as a percent)	50.00%
Minimum | First Target Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	$ 0.2125
Minimum | Second Target Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	0.24438
Minimum | Third Target Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	0.26563
Minimum | Thereafter Distributions
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	0.31875
Maximum | First Target Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	0.24438
Maximum | Second Target Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	0.26563
Maximum | Third Target Distribution
Distribution Made to Limited Partner [Line Items]
Intended quarterly distribution to limited partner (in dollars per unit)	$ 0.31875

Cash Distributions - Schedule o

Cash Distributions - Schedule of Cash Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 13, 2018	Aug. 14, 2018	May 15, 2018	Feb. 14, 2018	Nov. 14, 2017	Aug. 14, 2017	May 15, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Equity [Abstract]
Total Quarterly Distribution Per Unit (in dollars per share)									$ 0.3133		$ 0.3479	$ 0.3361	$ 0.3245	$ 0.3025	$ 0.2922	$ 0.2821
Total Quarterly Cash Distribution	$ 25,678	$ 24,176	$ 22,700	$ 21,489	$ 20,573	$ 19,698	$ 18,842	$ 94,044	$ 77,117	$ 59,690

Net Income Per Limited Partne_3

Net Income Per Limited Partner and General Partner Interest - Conversion of Subordinated Units (Details) - Subordinated Units	Nov. 15, 2017shares
Limited Partners' Capital Account [Line Items]
Units outstanding (in units)	29,163,121
Conversion ratio	100.00%

Net Income Per Limited Partne_4

Net Income Per Limited Partner and General Partner Interest - Historical Earnings Per Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Limited Partners' Capital Account [Line Items]
Antidilutive securities excluded from computation of earnings per share	734	45,066
Net Income Attributable to General and Limited Partner Ownership Interest in CNX Midstream Partners LP	$ 134,042	$ 114,993	$ 96,486
Less: General partner interest in net income, including incentive distribution rights	13,387	5,614	2,526
Limited partner interest in net income	$ 120,655	$ 109,379	$ 93,960
Weighted average limited partner units outstanding — Basic
Weighted average limited partner units outstanding - basic (in units)	63,635,000	63,582,000	59,207,000
Weighted average limited partner units outstanding — Diluted
Weighted average limited partner units outstanding — diluted (in units)	63,694,000	63,634,000	59,289,000
Net income per limited partner unit — Basic
Net income per limited partner unit — Basic (in USD per unit)	$ 1.90	$ 1.72	$ 1.59
Net income per limited partner unit — Diluted
Net income per limited partner unit — diluted (in USD per unit)	$ 1.89	$ 1.72	$ 1.58
Common Units
Limited Partners' Capital Account [Line Items]
Limited partner interest in net income	$ 120,655	$ 70,837	$ 47,935
Weighted average limited partner units outstanding — Basic
Weighted average limited partner units outstanding - basic (in units)	63,635,000	41,710,000	30,044,000
Weighted average limited partner units outstanding — Diluted
Weighted average limited partner units outstanding — diluted (in units)	63,694,000	41,762,000	30,126,000
Net income per limited partner unit — Basic
Net income per limited partner unit — Basic (in USD per unit)	$ 1.90	$ 1.70	$ 1.60
Net income per limited partner unit — Diluted
Net income per limited partner unit — diluted (in USD per unit)	$ 1.89	$ 1.70	$ 1.59
Subordinated Units
Limited Partners' Capital Account [Line Items]
Limited partner interest in net income	$ 0	$ 38,542	$ 46,025
Weighted average limited partner units outstanding — Basic
Weighted average limited partner units outstanding - basic (in units)	0	21,872,000	29,163,000
Weighted average limited partner units outstanding — Diluted
Weighted average limited partner units outstanding — diluted (in units)	0	21,872,000	29,163,000
Net income per limited partner unit — Basic
Net income per limited partner unit — Basic (in USD per unit)	$ 0	$ 1.76	$ 1.58
Net income per limited partner unit — Diluted
Net income per limited partner unit — diluted (in USD per unit)	$ 0	$ 1.76	$ 1.58

Related Party Transaction (Deta

Related Party Transaction (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Property and equipment, net	$ 891,775	$ 899,278
Proceeds from sale of assets	6,462	21,531	$ 5,332
Noncash contribution of assets held by general partner	3,105	$ 5,054
CNX Gathering LLC | Affiliated Entity
Related Party Transaction [Line Items]
Noncash contribution of assets held by general partner	5,000
Additional Systems | CNX | Affiliated Entity
Related Party Transaction [Line Items]
Property and equipment, net	17,400
Proceeds from sale of assets	14,000
Loss on asset sales	$ 3,400

Related Party Transaction - Sch

Related Party Transaction - Schedule of Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
General and administrative expense — related party	$ 13,867	$ 10,750	$ 10,446
Operating Expense | Affiliated Entity
Related Party Transaction [Line Items]
Charges for services	19,814	25,513	29,771
General and Administrative Expense | Affiliated Entity
Related Party Transaction [Line Items]
General and administrative expense — related party	13,867	10,750	10,446
CNX | Operating Expense | Affiliated Entity | Shared Service Agreement
Related Party Transaction [Line Items]
Charges for services	12,739	13,166	12,875
CNX | General and Administrative Expense | Affiliated Entity | Shared Service Agreement
Related Party Transaction [Line Items]
General and administrative expense — related party	13,867	10,167	9,796
CNX Resources And Noble Energy | Operating Expense | Affiliated Entity | Electrically-powered Compression Reimbursement
Related Party Transaction [Line Items]
Charges for services	7,075	12,347	16,896
Noble Energy | General and Administrative Expense | Affiliated Entity
Related Party Transaction [Line Items]
General and administrative expense — related party	$ 0	$ 583	$ 650

Related Party Transaction - Rel

Related Party Transaction - Related Party Receivables and Payables (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Accounts payable — related party	$ 4,980	$ 2,376
CNX
Related Party Transaction [Line Items]
Accounts payable — related party	4,980	2,321
Noble Energy
Related Party Transaction [Line Items]
Accounts payable — related party	0	55
Expense reimbursements | CNX
Related Party Transaction [Line Items]
Accounts payable — related party	1,143	780
Capital expenditures reimbursements | CNX
Related Party Transaction [Line Items]
Accounts payable — related party	182	83
General and administrative services | CNX
Related Party Transaction [Line Items]
Accounts payable — related party	3,655	1,458
General and administrative services | Noble Energy
Related Party Transaction [Line Items]
Accounts payable — related party	$ 0	$ 55

Related Party Transaction - Omn

Related Party Transaction - Omnibus Agreement (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
CNX | Affiliated Entity | Administrative Services
Related Party Transaction [Line Items]
General and administrative expenses	$ 1.9

Related Party Transaction - Ope

Related Party Transaction - Operational Services Agreement (Details) - CNX - Affiliated Entity - Operational Service Agreement	12 Months Ended
	Dec. 31, 2018
Related Party Transaction [Line Items]
Termination period to either party	6 months
Termination period	180 days
Maximum period to cure default	45 days

Related Party Transaction - Gat

Related Party Transaction - Gathering Agreements (Details) $ in Millions	May 02, 2018well	Jan. 03, 2018well$ / MMBTU	Apr. 30, 2022USD ($)well	Apr. 30, 2021USD ($)well	Dec. 31, 2018USD ($)well$ / bbl$ / MMBTU	Apr. 30, 2020USD ($)well	Dec. 31, 2020USD ($)well	Dec. 31, 2023USD ($)well	Jan. 01, 2018$ / MMBTU
Related Party Transaction [Line Items]
Related Party Transaction, Minimum Volume Commitment, Gas Gathering Fee					0.35
Downstream fees receivable (in dollars per MMBtu)					0.593
Conditional increase, percent					2.50%
Maximum change in fees, commencing January 1, 2035, percent					3.00%
Marcellus Shale formation
Related Party Transaction [Line Items]
Fees receivable, excluding downstream (in dollars per MMBtu)					0.431
Pittsburgh International Airport area
Related Party Transaction [Line Items]
Downstream fees receivable (in dollars per MMBtu)					0.296
Shirley-Penns area
Related Party Transaction [Line Items]
Condensate fees receivable (in dollars per Bbl) | $ / bbl					5.38
Majorsville Area
Related Party Transaction [Line Items]
Condensate fees receivable (in dollars per Bbl) | $ / bbl					5.38
Utica Shale formation | Gas Gathering Agreements
Related Party Transaction [Line Items]
Downstream fees receivable, weighted average (in dollars per MMBtu)					0.15
CNX Gas | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Term of agreement		20 years
Termination period to either party		180 days
CNX Gas | Utica Shale, McQuay Area | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Gas gathering fee (in dollars per MMBtu)		0.225
CNX Gas | Marcellus and Utical Shale, Wadestown Area | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Gas gathering fee (in dollars per MMBtu)		0.35
CNX Gas | McQuay And Wadestown Areas | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Compression fee, tier 1 pressure services, maximum of 600 psi (in dollars per MMBtu)									0.065
Compression fee, tier 2 pressure services, maximum of 300 psi (in dollars per MMBtu									0.130
CNX Gas | Marcellus Shale formation | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Number of wells drilled and completed (in wells) | well		125			30
Deficiency payment, per well | $					$ 3.5
CNX Gas | Majorsville And Mamont Areas | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Number of wells drilled and completed (in wells) | well	40
Subsequent Event | CNX Gas | Marcellus Shale formation | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Number of wells drilled and completed (in wells) | well			30	40		40
Deficiency payment, per well | $			$ 2	$ 2		$ 3.5
Subsequent Event | CNX Gas | Majorsville And Mamont Areas | Affiliated Entity | Gas Gathering Agreements
Related Party Transaction [Line Items]
Number of wells drilled and completed (in wells) | well							15	25
Deficiency payment, per well | $							$ 2.8	$ 2.8

Related Party Transaction - Reg

Related Party Transaction - Registration Rights Agreement (Details) - shares	Sep. 26, 2018	Jun. 29, 2018
Noble Energy
Related Party Transaction [Line Items]
Sale of units (in units)	14,217,198	7,475,000

Related Party Transaction - S_2

Related Party Transaction - Schedule of MVC per Gathering Agreements (Details) (Details) $ in Millions	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 21.4
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 34.7
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 40.8
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 47.8
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 42.9
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied	$ 401.3
Performance obligations expected to be satisfied, expected timing

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 974,394	$ 972,841
Less — accumulated depreciation	82,619	73,563
Property and Equipment — Net	891,775	899,278
Land
Property, Plant and Equipment [Line Items]
Property and equipment	67,624	76,130
Gathering equipment
Property, Plant and Equipment [Line Items]
Property and equipment	605,722	662,595
Less — accumulated depreciation	$ 58,561	53,544
Gathering equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years
Gathering equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years
Compression equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 199,728	180,038
Less — accumulated depreciation	$ 18,099	14,886
Compression equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	30 years
Compression equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years
Processing equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 30,979	30,979
Less — accumulated depreciation	$ 5,959	5,133
Estimated useful lives	40 years
Assets under construction
Property, Plant and Equipment [Line Items]
Property and equipment	$ 70,341	$ 23,099

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Assets under construction
Property, Plant and Equipment [Line Items]
Partnership capitalized interest	$ 1.1	$ 0

Revolving Credit Facility - Nar

Revolving Credit Facility - Narrative (Details)	Mar. 08, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2014USD ($)
Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility	$ 600,000,000			$ 250,000,000
Additional borrowing capacity available	$ 250,000,000
Interest Expense, Debt		$ 2,400,000
Maximum secured leverage ratio		3.50
Minimum interest coverage ratio		2.50
Long term line of credit		$ 84,000,000	$ 149,500,000
Credit facility interest rate		4.21%	3.11%
Remaining borrowing capacity		$ 480,000,000
Revolving Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage		0.375%
Maximum total leverage ratio		4.75
Debt Instrument, Covenant, Maximum, Aggregate Unsecured Notes		$ 150,000,000
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage		0.50%
Maximum total leverage ratio		5.50
Revolving Credit Facility | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Revolving Credit Facility | Base Rate, London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Revolving Credit Facility | LIBOR plus 1% | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%
Revolving Credit Facility | LIBOR plus 1% | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.75%
Letter of Credit
Debt Instrument [Line Items]
Revolving credit facility	$ 100,000,000

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - USD ($) $ in Thousands	Mar. 15, 2024	Mar. 15, 2021	Mar. 16, 2018	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt				$ 393,215	$ 0
Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross			$ 400,000	400,000
Stated rate			6.50%
Long-term debt			$ 393,000	$ 393,215
Percent of principal amount able to be redeemed			35.00%
Redemption price including premium, percent			106.50%
Redemption price of principal, percent			100.00%
Change of control, cash payment of aggregate principal amount repurchased, percentage			101.00%
Scenario, Forecast | Senior Notes
Debt Instrument [Line Items]
Redemption price including premium, percent	100.00%	104.875%
Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of debt			$ 250,000

Long-Term Debt - Schedule of De

Long-Term Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Mar. 16, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt	$ 393,215		$ 0
Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	400,000	$ 400,000
Less: Unamortized debt issuance costs	1,410
Less: Unamortized bond discount	5,375
Long-term debt	$ 393,215	$ 393,000

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
For the year ending December 31, 2019	$ 6,637
For the year ending December 31, 2020	4,755
Total future minimum lease payments	$ 11,392

Commitments and Contingencies_2

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Rental expense	$ 7.9	$ 7.6	$ 7.7

Segment Information - Narrative

Segment Information - Narrative (Details) - segment	Mar. 16, 2018	Sep. 30, 2018	May 02, 2018	May 03, 2018	Mar. 15, 2018
Segment Reporting Information [Line Items]
Number of operating segments			3
Shirley-Penns System | Anchor Systems
Segment Reporting Information [Line Items]
Ownership interest	100.00%
Shirley-Penns System | Additional Systems
Segment Reporting Information [Line Items]
Noncontrolling interest, percent					95.00%
Shirley-Penns System | Anchor Systems
Segment Reporting Information [Line Items]
Ownership interest		100.00%
Shirley-Penns System | Additional Systems
Segment Reporting Information [Line Items]
Ownership interest		5.00%
Noncontrolling interest, ownership percentage by parent					5.00%
Exchange Transaction | Growth Systems
Segment Reporting Information [Line Items]
Noncontrolling interest, percent				5.00%
Moundsville | Exchange Transaction
Segment Reporting Information [Line Items]
Noncontrolling interest, percent				5.00%

Segment Information - Schedule

Segment Information - Schedule of Segment Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gathering Revenue	$ 256,668	$ 233,848	$ 239,211
Net Income (Loss)	138,995	134,062	130,122
Depreciation Expense	21,939	22,692	21,201
Capital Expenditures for Segment Assets	145,331	48,366	50,660
Segment Assets	925,428	926,589
Anchor Systems
Segment Reporting Information [Line Items]
Gathering Revenue	240,445	209,470	215,492
Net Income (Loss)	139,386	129,486	132,221
Depreciation Expense	19,009	17,008	16,132
Capital Expenditures for Segment Assets	136,615	46,393	41,451
Segment Assets	832,885	694,942
Growth Systems
Segment Reporting Information [Line Items]
Gathering Revenue	2,572	8,152	10,359
Net Income (Loss)	379	607	(6,624)
Depreciation Expense	748	2,193	2,157
Capital Expenditures for Segment Assets	120	702	1,089
Segment Assets	0	92,659
Additional Systems
Segment Reporting Information [Line Items]
Gathering Revenue	13,651	16,226	13,360
Net Income (Loss)	(770)	3,969	4,525
Depreciation Expense	2,182	3,491	2,912
Capital Expenditures for Segment Assets	8,596	1,271	$ 8,120
Segment Assets	$ 92,543	$ 138,988

Long-Term Incentive Plan - Narr

Long-Term Incentive Plan - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	2 years
Costs not yet recognized	$ 1.3
Long-Term Incentive Plan of 2014 | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Long-Term Incentive Plan of 2014 | Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Annual vesting percentage	33.00%
Long-Term Incentive Plan of 2014 | Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Annual vesting percentage	33.00%
Long-Term Incentive Plan of 2014 | Stock Compensation Plan | Common Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common units authorized	5,800,000
Long-Term Incentive Plan of 2014 | Phantom Share Units (PSUs) | Common Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit based compensation	$ 2.4	$ 1.2	$ 0.8

Long-Term Incentive Plan - Sche

Long-Term Incentive Plan - Schedule of Awarded and Unvested Units (Details) - Common Units - Long-Term Incentive Plan of 2014 - Phantom Share Units (PSUs)	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Number of Units
Total awarded and unvested at Period Start (in units) | shares	134,153
Granted (in units) | shares	139,234
Vested (in units) | shares	(72,469)
Forfeited (in units) | shares	(22,289)
Total awarded and unvested at Period End (in units) | shares	178,629
Weighted Average Grant Date Fair Value
Total awarded and unvested, beginning balance (usd per share) | $ / shares	$ 16.40
Granted (usd per share) | $ / shares	19.14
Vested (usd per share) | $ / shares	16.64
Forfeited (usd per share) | $ / shares	16.59
Total awarded and unvested, ending balance (usd per share) | $ / shares	$ 18.35

Subsequent Events (Details)

Subsequent Events (Details)	Jan. 16, 2019$ / shares
Subsequent Event
Subsequent Event [Line Items]
Cash distribution declared to Partnership's unitholders (in dollars per unit)	$ 0.3603