Consolidated Entities and Equity Method Investments - Investment in SNG (Details) - SNG - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement Information
Revenues	$ 155	$ 146	$ 321	$ 306
Operating income	86	60	192	159
Net income	$ 64	$ 54	$ 148	$ 132

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

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