Goodwill and Other Intangible Assets - Schedule of Other Intangible Assets (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended						12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018	[1]	Jun. 30, 2018	[1]	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Other intangibles amortization	$ 27	[1]	$ 25		$ 10		$ 62
Other Intangible Assets [Member]
Finite Lived Intangible Assets [Line Items]
Other intangibles amortization							62
Amortization expense for intangible assets, in 2019	87						87
Amortization expense for intangible assets, in 2020	87						87
Amortization expense for intangible assets, in 2021	81						81
Amortization expense for intangible assets, in 2022	74						74
Amortization expense for intangible assets, in 2023	$ 68						$ 68

[1] Represents amortization of other intangible assets acquired in the Combination. See Note 9, Goodwill and Other Intangible Assets, for further discussion.