Investment in Unconsolidated Affiliates Summarized Balance Sheet Information of Equity Method Investment (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Summarized Balance Sheet Information of Equity Method Investment [Abstract]
Current assets	$ 417	$ 449
Non-current assets	12,018	11,995
Current liabilities	819	1,615
Non-current liabilities	$ 4,076	$ 3,211

Summarized Balance Sheet Information of Equity Method Investment [Abstract]

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The amount of current assets reported by an equity method investment of the entity.

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