Intangible Assets - Schedule of Project Related Intangibles (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Project related intangible assets, Gross Carrying Amount	$ 239
Project related intangible assets, Accumulated Amortization	(63)
Project related intangible assets, Net Carrying Amount	$ 176
Project related intangible assets, Accumulated Amortization	3 years
Project related intangible liabilities, Gross Carrying Amount	$ (97)
Project related intangible liabilities, Accumulated Amortization	21
Project related intangible liabilities, Net Carrying Amount	$ (76)
Project related intangible liabilities, Weighted Average Life	2 years
Total, Gross Carrying Amount	$ 142	[1]
Total, Accumulated Amortization	(42)	[1]
Total, Net Carrying Amount	$ 100	[1]

[1] All project related intangible assets at September 30, 2018 resulted from the Combination. Amortization expense was $30 million and $42 million for the three and nine months ended September 30, 2018, respectively, and is anticipated to be $31 million, $33 million, $22 million, $5 million and $7 million for the remainder of 2018, 2019, 2020, 2021 and 2022, respectively