Segment Information - Reconciliation of Reportable Segment Operating Margin to Income (Loss) Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	$ 383.2	$ 341.4
Depreciation and amortization expense	(237.4)	(198.1)
General and administrative expense	(81.1)	(56.7)
Interest income (expense), net	(80.6)	16.1
Change in contingent considerations	(9.7)	(56.1)
Other, net	(2.0)	1.2
Income (loss) before income taxes	(27.6)	47.8
Gathering and Processing [Member]
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	229.0	220.8
Logistics and Marketing [Member]
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	152.1	138.4
Other Segment [Member]
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	$ 2.1	$ (17.8)

Revenues reduced by product purchases and operating expenses.

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Other operating and non operating income expense net.

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Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement.

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- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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The net amount of nonoperating interest income (expense).

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