Number of miles the pipeline is operated.

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The cash outflow associated with additional investments in or advances to an entity in which the reporting entity shares control of the entity with another party or group. Excludes initial investment.

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The cash outflow associated with the initial investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

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Percentage of interest held in third party assets by our joint venture.

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No definition available.

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Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

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Monetary value of the issuance of new units of limited partnership interest in a public offering, net of offering costs. This is a parenthetical disclosure.

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The number of units sold in a public offering of each class of partners' capital account. Units represent shares of ownership of the general, limited, and preferred partners.

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The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Equity Method Investments (Details) $ in Thousands			3 Months Ended		9 Months Ended
Equity Method Investments (Details) $ in Thousands	Feb. 10, 2017 USD ($) shares	Feb. 06, 2017	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 mi
Equity Method Investment
Contribution to joint venture					$ 216,776	$ 45,044
Investments in unconsolidated affiliates
Balance at beginning of period					68,299
Initial investment					153,770
Additional investment					63,006
Equity in net income (loss) of unconsolidated affiliates			$ 7,033	$ 1,544	12,887	$ 2,027
Distributions from unconsolidated affiliates					(10,120)
Balance at end of period			287,842		287,842
Common Unitholders Public
Equity Method Investment
Sale of units to public (in shares) \| shares	6,900,000
Net proceeds from sale of units	$ 223,000
Appalachia Joint venture
Equity Method Investment
Ownership percentage		50.00%
Percentage of interest held by joint venture in third party fractionator in Ohio		33.33%
Investments in unconsolidated affiliates
Initial investment					153,770
Additional investment					63,006
Equity in net income (loss) of unconsolidated affiliates					5,218
Distributions from unconsolidated affiliates					(1,660)
Balance at end of period			$ 220,334		$ 220,334
Appalachia Joint venture \| MarkWest
Equity Method Investment
Ownership percentage		50.00%	50.00%		50.00%
Stonewall Gas Gathering LLC
Equity Method Investment
Ownership percentage			15.00%		15.00%		15.00%
Number of miles \| mi							67
Investments in unconsolidated affiliates
Balance at beginning of period					$ 68,299
Equity in net income (loss) of unconsolidated affiliates					7,669
Distributions from unconsolidated affiliates					(8,460)
Balance at end of period			$ 67,508		$ 67,508