Investment in Unconsolidated Affiliates Summarized Income Statement of Equity Method Investment (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 735.0	$ 805.0	$ 1,530.0	$ 1,553.0
Cost of natural gas and NGLs	317.0	444.0	695.0	819.0
Operating income	167.0	126.0	332.0	265.0
Net income	$ 114.8	$ 86.4	$ 228.0	$ 191.0

Equity Method Investment, Summarized Financial Information, Operating Income

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The amount of the cost of sales reported by an equity method investment of the entity.

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The amount of net income (loss) reported by an equity method investment of the entity.

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Amount of revenue from sale of product and rendering of service reported by equity method investee.

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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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