Stockholders' Equity and Equity-Based Incentive Plans - Changes in the Number of Shares Outstanding and Treasury Shares Held by the Company (Detail) - shares shares in Millions	9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Dec. 31, 2018
Shares Outstanding [Abstract]
Beginning balance	181		95
Common stock issued	2		2
Shares issued in the Combination (Note 3, Business Combination)			85
Purchase of common stock	(1)		(1)
Ending balance	182		181
Shares Held as Treasury Shares [Abstract]
Beginning balance	3		3
Purchase of common stock	1		1
Retirement of common stock	(1)		(1)
Ending balance	3		3
Common stock, shares issued	185	[1]	183	[1]	183

[1] ^{Amounts in this table may not sum due to rounding.}