Intangible Assets - Schedule of Project Related Intangibles (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Project related intangible assets, Gross Carrying Amount	$ 145
Project related intangible assets, Accumulated Amortization	$ (16)
Project related intangible assets, Accumulated Amortization	3 years
Project related intangible liabilities, Gross Carrying Amount	$ (33)
Project related intangible liabilities, Accumulated Amortization	$ 4
Project related intangible liabilities, Weighted Average Life	2 years
Total, Gross Carrying Amount	$ 112	[1]
Total, Accumulated Amortization	$ (12)	[1]

[1] All project related intangible assets at June 30, 2018 resulted from the Combination. Amortization expense was $12 million for the three months ended June 30, 2018 and is anticipated to be $42 million, $27 million, $19 million and $12 million for the remainder of 2018, 2019, 2020 and 2021, respectively