Significant Accounting Policies - Changes in Accumulated Other Comprehensive Loss Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 9,084	$ 8,877	$ 9,456	$ 8,036
Other comprehensive earnings (loss), net of tax	3	1	4	1
Ending Balance	9,366	8,840	9,366	8,840
Pension and Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(8)	(47)	(9)	(48)
Other comprehensive earnings (loss) before reclassifications, net of tax	0		0	0
Amounts reclassified from accumulated other comprehensive loss, net of tax	1	1	2	2
Other comprehensive earnings (loss), net of tax	1	1	2	2
Ending Balance	(7)	(46)	(7)	(46)
Foreign Currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(4)	(2)	(4)	(1)
Other comprehensive earnings (loss) before reclassifications, net of tax	2		2	(1)
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0	0	0
Other comprehensive earnings (loss), net of tax	2	0	2	(1)
Ending Balance	(2)	(2)	(2)	(2)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(12)	(49)	(13)	(49)
Other comprehensive earnings (loss) before reclassifications, net of tax	2		2	(1)
Amounts reclassified from accumulated other comprehensive loss, net of tax	1	1	2	2
Other comprehensive earnings (loss), net of tax	3	1	4	1
Ending Balance	$ (9)	$ (48)	$ (9)	$ (48)