Investments in Unconsolidated Affiliates - Equity Method Investment Summarized Financial Information, Statement of Operations (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Operating revenue	$ 523	$ 438	$ 1,560	$ 1,291
Operating expenses	196	167	572	520
Net income	$ 326	$ 271	$ 985	$ 771

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

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