Debt - Classification and Credit Facilities (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Debt
Debt maturing or subject to remarketing within twelve months	$ 3,800
Debt classified as long-term due to intent and ability to refinance on long-term basis	2,800
Current portion of long-term debt	$ 954	$ 1,359
Minimum [Member]
Debt
Spread rate (as a percent)	0.585%
Maximum [Member]
Debt
Spread rate (as a percent)	1.025%
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	$ 1,300
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)	4.80%	4.80%
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	$ 454
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
Other Letter Of Credit Lines [Member]
Debt
Letters of credit outstanding	$ 860