Employee Benefit Plans and Equity Compensation Plan (Changes in Benefit Obligations) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance	$ 580	$ 702
Service cost	8	8	$ 9
Interest cost	33	21	20
Amendments	1	0
Actuarial (gain) loss	1	(105)
Benefits paid	(39)	(46)
Ending balance	584	580	702
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning balance	121	171
Service cost	1	1	1
Interest cost	8	6	6
Amendments	0	0
Actuarial (gain) loss	1	(44)
Benefits paid	(11)	(13)
Ending balance	$ 120	$ 121	$ 171