Debt - Classification and Credit Facilities (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Debt
Debt maturing or subject to remarketing within twelve months	$ 4,000
Debt classified as long-term due to intent and ability to refinance on long-term basis	3,000
Current portion of long-term debt	964	$ 1,359
Tax Exempt Bonds [Member]
Debt
Debt maturing or subject to remarketing within twelve months	298
Debt with interest rate periods that expire in the next 12 months	$ 1,500
Tax Exempt Bonds [Member] | Minimum [Member]
Debt
Interest rate (as a percent)	0.70%	0.70%
Tax Exempt Bonds [Member] | Maximum [Member]
Debt
Interest rate (as a percent)	4.60%	4.60%
Commercial Paper Program [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 1,500
Debt term	397 days
Commercial paper borrowings	$ 1,500
0.750% senior notes due 2025 [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 500
Interest rate (as a percent)	0.75%
Financing leases and other [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 464
Revolving Credit Facility [Member]
Debt
Maximum capacity	3,500
Outstanding borrowings under credit facility	0
Letters of credit outstanding	224
Unused and available credit capacity	$ 1,800
Revolving Credit Facility [Member] | Minimum [Member]
Debt
Spread rate (as a percent)	0.585%
Revolving Credit Facility [Member] | Maximum [Member]
Debt
Spread rate (as a percent)	1.025%
Other Letter Of Credit Lines [Member]
Debt
Letters of credit outstanding	$ 870