Significant Accounting Policies - Changes in Accumulated Other Comprehensive Loss Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 9,456	$ 8,036
Other comprehensive earnings (loss), net of tax	1	0
Ending Balance	9,084	8,877
Pension and Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9)	(48)
Other comprehensive loss before reclassifications, net of tax		0
Amounts reclassified from accumulated other comprehensive loss, net of tax	1	1
Other comprehensive earnings (loss), net of tax	1	1
Ending Balance	(8)	(47)
Foreign Currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4)	(1)
Other comprehensive loss before reclassifications, net of tax		(1)
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0
Other comprehensive earnings (loss), net of tax	0	(1)
Ending Balance	(4)	(2)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(13)	(49)
Other comprehensive loss before reclassifications, net of tax		(1)
Amounts reclassified from accumulated other comprehensive loss, net of tax	1	1
Other comprehensive earnings (loss), net of tax	1	0
Ending Balance	$ (12)	$ (49)