Debt and Interest Rate Derivatives - Debt classification and Utilization (Detail) - USD ($) $ in Millions		9 Months Ended
	Jul. 28, 2020	Sep. 30, 2020	Dec. 31, 2019
Debt
Debt maturing or subject to remarketing within twelve months		$ 2,200
Current portion of long-term debt		167	$ 218
4.60% senior notes due March 2021 [Member]
Debt
Debt instrument face amount		$ 400
Interest rate (as a percent)		4.60%
Tax Exempt Bonds [Member]
Debt
Current portion of long-term debt		$ 63
Debt with interest rate periods that expire in the next 12 months		952
Debt maturing or subject to remarketing within twelve months classified as long-term		2,000
Variable-rate tax-exempt bonds		54
Variable-rate tax-exempt bonds, non-current		$ 54
Tax Exempt Bonds [Member] | Minimum [Member]
Debt
Interest rate (as a percent)		0.17%
Tax Exempt Bonds [Member] | Maximum [Member]
Debt
Interest rate (as a percent)		4.30%
Financing leases and other [Member]
Debt
Current portion of long-term debt		$ 167
$3.0 billion US revolving credit facility [Member]
Debt
Maximum capacity	$ 3,000
Debt term	364 days
Outstanding borrowings under credit facility		$ 0
$3.0 billion US revolving credit facility [Member] | London Interbank Offered Rate [Member]
Debt
Spread rate		1.225%
$3.0 billion US revolving credit facility [Member] | London Interbank Offered Rate [Member] | Minimum [Member]
Debt
Spread rate	1.00%
$3.0 billion US revolving credit facility [Member] | London Interbank Offered Rate [Member] | Maximum [Member]
Debt
Spread rate	1.30%
$3.5 billion revolving credit facility [Member]
Debt
Maximum capacity		$ 3,500
Outstanding borrowings under credit facility		0
Letters of credit outstanding		269
Unused and available credit capacity		2,600
Commercial Paper Program [Member]
Debt
Current portion of long-term debt		$ 600
Debt term		397 days
Commercial paper borrowings		$ 600
Other Letter Of Credit Facilities [Member]
Debt
Letters of credit outstanding		$ 528