Intangible Assets - Schedule of Project Related Intangibles (Parenthetical) (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Finite Lived Intangible Assets [Line Items]
Other intangibles amortization	$ 25	$ 35
Project Related Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Other intangibles amortization	30	42
Amortization expense for intangible assets, remainder of 2018	31	31
Amortization expense for intangible assets, in 2019	33	33
Amortization expense for intangible assets, in 2020	22	22
Amortization expense for intangible assets, in 2021	5	5
Amortization expense for intangible assets, in 2022	$ 7	$ 7