Operating Revenue (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disaggregation Of Revenue [Line Items]
Contract liability balances	$ 7	$ 12
Revenue recognized from contract liability balances	$ 9	$ 6
Minimum [Member]
Disaggregation Of Revenue [Line Items]
Service Contract, Term	10 years
Maximum [Member]
Disaggregation Of Revenue [Line Items]
Service Contract, Term	15 years