Long-Term Debt (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Credit Facility	$ 2,500	$ 0
Finance lease obligations	156	157
Total debt	12,233	10,940
Less: Current portion of long-term debt	(1,664)	(977)
Long-term debt, noncurrent	10,569	9,963
Series L Notes, interest rate of 3.3%, face amount of $350, maturing September 15, 2022 (effective interest rate of 3.4%)
Debt Instrument [Line Items]
Senior notes	349	349
Series M Notes, interest rate of 3.4%, face amount of $350, maturing October 15, 2020 (effective interest rate of 3.6%)
Debt Instrument [Line Items]
Senior notes	350	349
Series N Notes, interest rate of 3.1%, face amount of $400, maturing October 15, 2021 (effective interest rate of 3.4%)
Debt Instrument [Line Items]
Senior notes	399	398
Series O Notes, interest rate of 2.9%, face amount of $450, maturing March 1, 2021 (effective interest rate of 3.1%)
Debt Instrument [Line Items]
Senior notes	449	449
Series P Notes, interest rate of 3.8%, face amount of $350, maturing October 1, 2025 (effective interest rate of 4.0%)
Debt Instrument [Line Items]
Senior notes	346	346
Series Q Notes, interest rate of 2.3%, face amount of $750, maturing January 15, 2022 (effective interest rate of 2.5%)
Debt Instrument [Line Items]
Senior notes	747	747
Series R Notes, interest rate of 3.1%, face amount of $750, maturing June 15, 2026 (effective interest rate of 3.3%)
Debt Instrument [Line Items]
Senior notes	744	744
Series U Notes, interest rate of 3.1%, face amount of $291, maturing February 15, 2023 (effective interest rate of 3.1%)
Debt Instrument [Line Items]
Senior notes	291	291
Series V Notes, interest rate of 3.8%, face amount of $318, maturing March 15, 2025 (effective interest rate of 2.8%)
Debt Instrument [Line Items]
Senior notes	332	332
Series W Notes, interest rate of 4.5%, face amount of $278, maturing October 1, 2034 (effective interest rate of 4.1%)
Debt Instrument [Line Items]
Senior notes	291	291
Series X Notes, interest rate of 4.0%, face amount of $450, maturing April 15, 2028 (effective interest rate of 4.2%)
Debt Instrument [Line Items]
Senior notes	444	444
Series Y Notes, floating rate, face amount of $550, maturing December 1, 2020 (effective interest rate of 2.2% at March 31, 2020)
Debt Instrument [Line Items]
Senior notes	549	549
Series Z Notes, interest rate of 4.2%, face amount of $350, maturing December 1, 2023 (effective interest rate of 4.4%)
Debt Instrument [Line Items]
Senior notes	348	347
Series AA Notes, interest rate of 4.7%, face amount of $300, maturing December 1, 2028 (effective interest rate of 4.8%)
Debt Instrument [Line Items]
Senior notes	297	297
Series BB Notes, floating rate, face amount of $300, maturing March 8, 2021 (effective interest rate of 1.6% at March 31, 2020)
Debt Instrument [Line Items]
Senior notes	299	299
Series CC Notes, interest rate of 3.6%, face amount of $550, maturing April 15, 2024 (effective interest rate of 3.9%)
Debt Instrument [Line Items]
Senior notes	591	564
Series DD Notes, interest rate of 2.1%, face amount of $550, maturing October 3, 2022 (effective interest rate of 2.4%)
Debt Instrument [Line Items]
Senior notes	$ 561	543
Senior Notes \| Series L Notes, interest rate of 3.3%, face amount of $350, maturing September 15, 2022 (effective interest rate of 3.4%)
Debt Instrument [Line Items]
Interest rate	3.30%
Senior notes, face amount	$ 350
Effective interest rate	3.40%
Senior Notes \| Series M Notes, interest rate of 3.4%, face amount of $350, maturing October 15, 2020 (effective interest rate of 3.6%)
Debt Instrument [Line Items]
Interest rate	3.40%
Senior notes, face amount	$ 350
Effective interest rate	3.60%
Senior Notes \| Series N Notes, interest rate of 3.1%, face amount of $400, maturing October 15, 2021 (effective interest rate of 3.4%)
Debt Instrument [Line Items]
Interest rate	3.10%
Senior notes, face amount	$ 400
Effective interest rate	3.40%
Senior Notes \| Series O Notes, interest rate of 2.9%, face amount of $450, maturing March 1, 2021 (effective interest rate of 3.1%)
Debt Instrument [Line Items]
Interest rate	2.90%
Senior notes, face amount	$ 450
Effective interest rate	3.10%
Senior Notes \| Series P Notes, interest rate of 3.8%, face amount of $350, maturing October 1, 2025 (effective interest rate of 4.0%)
Debt Instrument [Line Items]
Interest rate	3.80%
Senior notes, face amount	$ 350
Effective interest rate	4.00%
Senior Notes \| Series Q Notes, interest rate of 2.3%, face amount of $750, maturing January 15, 2022 (effective interest rate of 2.5%)
Debt Instrument [Line Items]
Interest rate	2.30%
Senior notes, face amount	$ 750
Effective interest rate	2.50%
Senior Notes \| Series R Notes, interest rate of 3.1%, face amount of $750, maturing June 15, 2026 (effective interest rate of 3.3%)
Debt Instrument [Line Items]
Interest rate	3.10%
Senior notes, face amount	$ 750
Effective interest rate	3.30%
Senior Notes \| Series U Notes, interest rate of 3.1%, face amount of $291, maturing February 15, 2023 (effective interest rate of 3.1%)
Debt Instrument [Line Items]
Interest rate	3.10%
Senior notes, face amount	$ 291
Effective interest rate	3.10%
Senior Notes \| Series V Notes, interest rate of 3.8%, face amount of $318, maturing March 15, 2025 (effective interest rate of 2.8%)
Debt Instrument [Line Items]
Interest rate	3.80%
Senior notes, face amount	$ 318
Effective interest rate	2.80%
Senior Notes \| Series W Notes, interest rate of 4.5%, face amount of $278, maturing October 1, 2034 (effective interest rate of 4.1%)
Debt Instrument [Line Items]
Interest rate	4.50%
Senior notes, face amount	$ 278
Effective interest rate	4.10%
Senior Notes \| Series X Notes, interest rate of 4.0%, face amount of $450, maturing April 15, 2028 (effective interest rate of 4.2%)
Debt Instrument [Line Items]
Interest rate	4.00%
Senior notes, face amount	$ 450
Effective interest rate	4.20%
Senior Notes \| Series Y Notes, floating rate, face amount of $550, maturing December 1, 2020 (effective interest rate of 2.2% at March 31, 2020)
Debt Instrument [Line Items]
Senior notes, face amount	$ 550
Effective interest rate	2.20%
Senior Notes \| Series Z Notes, interest rate of 4.2%, face amount of $350, maturing December 1, 2023 (effective interest rate of 4.4%)
Debt Instrument [Line Items]
Interest rate	4.20%
Senior notes, face amount	$ 350
Effective interest rate	4.40%
Senior Notes \| Series AA Notes, interest rate of 4.7%, face amount of $300, maturing December 1, 2028 (effective interest rate of 4.8%)
Debt Instrument [Line Items]
Interest rate	4.70%
Senior notes, face amount	$ 300
Effective interest rate	4.80%
Senior Notes \| Series BB Notes, floating rate, face amount of $300, maturing March 8, 2021 (effective interest rate of 1.6% at March 31, 2020)
Debt Instrument [Line Items]
Senior notes, face amount	$ 300
Effective interest rate	1.60%
Senior Notes \| Series CC Notes, interest rate of 3.6%, face amount of $550, maturing April 15, 2024 (effective interest rate of 3.9%)
Debt Instrument [Line Items]
Interest rate	3.60%
Senior notes, face amount	$ 550
Effective interest rate	3.90%
Senior Notes \| Series DD Notes, interest rate of 2.1%, face amount of $550, maturing October 3, 2022 (effective interest rate of 2.4%)
Debt Instrument [Line Items]
Interest rate	2.10%
Senior notes, face amount	$ 550
Effective interest rate	2.40%
Commercial paper
Debt Instrument [Line Items]
Commercial paper	$ 2,011	3,197
Other
Debt Instrument [Line Items]
Other	$ 179	$ 247

Carrying value as of the balance sheet date of long-term unsecured obligations issued by corporations and other borrowers to investors (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

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