Investments in Unconsolidated Affiliates - Equity Method Investment Summarized Financial Information, Balance Sheet (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Current assets	$ 368		$ 463
Long-term assets	7,598		7,546
Current liabilities	(169)		(231)
Long-term liabilities	(257)		(252)
Net assets	7,540		$ 7,526
Operating revenue	527	$ 421
Operating expenses	185	191
Net income	$ 341	$ 231