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Income Tax (Tables) | 12 Months Ended
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Dec. 31, 2018
Income Tax Disclosure [Abstract] |
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] | The components of the “Provision/(benefit) for income taxes” are as follows:
| December 31,
(In millions) | 2018 |  | 2017 |  | 2016
Current income tax expense: |  |  |  |  |
Federal | $ | — |  |  | $ | — |  |  | $ | 4 |
State | — |  |  | 2 |  |  | 1 |
Total current | — |  |  | 2 |  |  | 5 |
Deferred income tax expense/(benefit): |  |  |  |  |
Federal | — |  |  | — |  |  | (16 | )
State | 8 |  |  | (1 | ) |  | (1 | )
Total deferred | 8 |  |  | (1 | ) |  | (17 | )
Provision/(benefit) for income taxes | $ | 8 |  |  | $ | 1 |  |  | $ | (12 | )
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] | A reconciliation of the “Provision/(benefit) for income taxes” and the amount computed by applying the federal statutory rate of 35 percent to the income before income taxes for the year ended December 31, 2016 is as follows:
|  | December 31, 2016
(In millions) |  | MarkWest Hydrocarbon(1) |  | Partnership |  | Eliminations |  | Consolidated
(Loss)/income before (benefit)/provision for income tax |  | $ | (41 | ) |  | $ | 461 |  |  | $ | 2 |  |  | $ | 422 |
Federal statutory rate |  | 35 | % |  | — | % |  | — | % |  |
Federal income tax at statutory rate |  | (14 | ) |  | — |  |  | — |  |  | (14 | )
State income taxes net of federal benefit |  | (2 | ) |  | 1 |  |  | — |  |  | (1 | )
Provision on income from MPLX LP Class A units |  | 3 |  |  | — |  |  | — |  |  | 3 |
Change in state statutory rate |  | (1 | ) |  | — |  |  | — |  |  | (1 | )
Other |  | 1 |  |  | — |  |  | — |  |  | 1 |
(Benefit)/provision for income taxes |  | $ | (13 | ) |  | $ | 1 |  |  | $ | — |  |  | $ | (12 | )
(1) | MarkWest Hydrocarbon paid tax on its share of MPLX’s income or loss as a result of its ownership of MPLX LP Class A units through September 1, 2016.

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- Definition Tabular disclosure of the components of income tax expense attributable to continuing operations for each year presented including, but not limited to: current tax expense (benefit), deferred tax expense (benefit), investment tax credits, government grants, the benefits of operating loss carryforwards, tax expense that results from allocating certain tax benefits either directly to contributed capital or to reduce goodwill or other noncurrent intangible assets of an acquired entity, adjustments of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity, and adjustments of the beginning-of-the-year balances of a valuation allowance because of a change in circumstances that causes a change in judgment about the realizability of the related deferred tax asset in future years. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 + Details
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- Definition Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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