Employee Benefits - Reconciliation of Beginning and Ending Balance of Pension Plan Assets Measured at Fair Value (Detail) - Pension - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	$ 13,536	$ 13,739
End of year	6,802	13,536
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	1,534	1,623
Actual gain (loss) on plan assets	(13)	(36)
Purchases (sales)	10	(20)
Transfers out	(10)	(33)
End of year	1,521	1,534
Level 3 | Equity securities
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	0
End of year	0	0
Level 3 | Corporate bonds
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	0
End of year	0	0
Level 3 | International bonds
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	0
End of year	0	0
Level 3 | Real estate
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	996	1,002
Actual gain (loss) on plan assets	(69)	(54)
Purchases (sales)	12	48
Transfers out	(5)	0
End of year	934	996
Level 3 | Private equity
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	512	569
Actual gain (loss) on plan assets	55	14
Purchases (sales)	(1)	(67)
Transfers out	(2)	(4)
End of year	564	512
Level 3 | Hedge funds
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning of year	26	52
Actual gain (loss) on plan assets	1	4
Purchases (sales)	(1)	(1)
Transfers out	(3)	(29)
End of year	$ 23	$ 26