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Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Feb. 28, 2013
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 3,368		$ 3,368		$ 2,471
Operational service revenue	$ 25	$ 24	$ 47	$ 45
MarkWest Utica EMG [Member]
Schedule of Equity Method Investments [Line Items]
Minimum Capital Contributed by Noncontrolling Owners						$ 950
Percentage of Required Capital Contribution by Reporting Entity after NCI						100.00%
Aggregate Contributions to VIE Threshold						$ 2,000
Percentage of Ownership Interest in Joint Venture, Maximum	70.00%		70.00%
Threshold Percentage of Noncontrolling Ownership Interest in Joint Venture	30.00%		30.00%
Maximum Percentage of Additional Noncontrolling Capital Contribution before Threshold Ownership			10.00%
Actual Capital Contributed by Noncontrolling Owners	$ 1,200		$ 1,200
Actual Capital Contribution to Date	$ 1,500		$ 1,500
Noncontrolling Owners Preference Threshold						$ 500
Noncontrolling Owners Accrual of Preference Amount		4		8
Percentage of aggregate investment balance	56.00%		56.00%
Equity method investments	$ 2,200		$ 2,200		$ 2,200
Operational service revenue	$ 4	5	$ 8	7
Equity Method Investment, Ownership Percentage	56.00%		56.00%
Ohio Gathering Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Operational service revenue	$ 4	$ 3	$ 8	$ 7
Equity Method Investment, Ownership Percentage	34.00%		34.00%

X

- Definition

This element represents the actual amount of the VIE's capital that the non-controlling interest owners have funded.

+ References

No definition available.

+ Details

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X

- Definition

The actual amount of the VIE's capital that has been funded by the reporting entity to date.

+ References

No definition available.

+ Details

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X

- Definition

Once the non-controlling interest owners have reached their required minimum capital contribution, this represents the aggregate amount of capital contributed to the VIE from all members that must be achieved before the non-controlling interest owners have the option to contribute additional capital.

+ References

No definition available.

+ Details

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- Definition

The maximum percentage of additional capital funding of the VIE the non-controlling interest owners have the right, but not obligation, to make after the aggregate contribution threshold from all members has been reached and until they reach their threshold ownership percentage for pro rata contributions.

+ References

No definition available.

+ Details

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X

- Definition

This element represents the amount of the VIE's capital requirements that the non-controlling interest owners are obligated to fund under the joint venture agreement.

+ References

No definition available.

+ Details

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X

- Definition

Represents the special non-cash allocation of income to non-controlling interest during the period.

+ References

No definition available.

+ Details

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- Definition

The minimum capital contributions (since inception) required of the non-controlling interest in order for it to receive a quarterly special allocation of income. The special allocation of income will be based only on amounts contributed in excess of this threshold and ends after the fifth year of the joint venture.

+ References

No definition available.

+ Details

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- Definition

Represents the maximum percentage to which the reporting entity can increase its ownership interest in the VIE, unless the non-controlling interest owners elect not to maintain their ownership interest.

+ References

No definition available.

+ Details

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X

- Definition

Represents the percentage of capital funding required of the reporting entity after the non-controlling interest owners have reached their required minimum capital contribution and until the aggregate contribution threshold has been reached.

+ References

No definition available.

+ Details

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- Definition

Percentage of aggregate investment balance

+ References

No definition available.

+ Details

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- Definition

Represents the threshold percentage of ownership interest in the VIE by the non-controlling interest owners, which upon reaching they have the option to maintain through pro rata capital contributions.

+ References

No definition available.

+ Details

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X

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

No definition available.

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- Definition

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.

+ References

No definition available.

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