Name:	mwe_BusinessAcquisitionCryogenicNaturalGasProcessingPlantCapacity
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Data Type:	xbrli:decimalItemType
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Represents the extended additional term of the keep-whole processing agreement.

No definition available.

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Data Type:	xbrli:durationItemType
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Period Type:	duration

Represents the length of natural gas gathering pipeline expressed in miles, acquired under the business combination entered into by the entity.

No definition available.

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Namespace Prefix:	mwe_
Data Type:	num:lengthItemType
Balance Type:	na
Period Type:	duration

Represents the length of rights-of-way associated with the future construction of a high-pressure trunk line expressed in miles, acquired under the business combination entered into by the entity.

No definition available.

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Namespace Prefix:	mwe_
Data Type:	num:lengthItemType
Balance Type:	na
Period Type:	duration

Represents the additional cash paid contemporaneously with business combination entered into by the entity as consideration for extension in term of the keep-whole processing agreement.

No definition available.

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Namespace Prefix:	mwe_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Area of land held.

No definition available.

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Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Details

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Data Type:	xbrli:stringItemType
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Period Type:	duration

Amount of liabilities incurred for goods and services received that are used in an entity's business and related party payables, assumed at the acquisition date.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of identifiable intangible assets recognized as of the acquisition date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 55

-Paragraph 37

-URI http://asc.fasb.org/extlink&oid=25498275&loc=d3e2207-128464

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Balance Type:	debit
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- Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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Period Type:	duration

The amount of property, plant, and equipment recognized as of the acquisition date.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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Data Type:	xbrli:monetaryItemType
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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585