Investment in Unconsolidated Affiliates Summarized Income Statement of Equity Method Investment (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 795.0	$ 748.0
Cost of natural gas and NGLs	378.0	375.0
Operating income	165.0	139.0
Net income	$ 113.2	$ 104.6

Equity Method Investment, Summarized Financial Information, Operating Income

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- Definition

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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- Definition

The amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.

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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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