Other Income, Net (Components of Other Income, Net) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Operating revenue from contracts with customers	$ 0	$ 0
Other income	2	3
Other expense	1	2
Allowance for equity funds used during construction	1	1
Other income, net	$ 4	$ 6