Other Financial Information - Schedule of Interest Cost Components (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Financial Information [Abstract]
Amount charged to expense	$ 122	$ 104	$ 243
Amount capitalized	14	17	23
Interest costs, total	$ 136	$ 121	$ 266