Long-Term Debt (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Credit Facility	$ 0	$ 0
Capital lease obligations	170	171
Total debt	8,846	8,238
Less: Current portion of long-term debt	(988)	(398)
Long-term debt, noncurrent	7,858	7,840
Series K Notes, interest rate of 3.0%, face amount of $600, maturing March 1, 2019 (effective interest rate of 4.4%)
Debt Instrument [Line Items]
Senior notes	598	598
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	348	348
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	348	348
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	397	397
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	448	447
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	345	345
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	744	744
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	743	743
Series S Notes, interest rate of 6.8%, face amount of $324, maturing May 15, 2018 (effective interest rate of 1.7%)
Debt Instrument [Line Items]
Senior notes	326	330
Series T Notes, interest rate of 7.2%, face amount of $181, maturing December 1, 2019 (effective interest rate of 2.3%)
Debt Instrument [Line Items]
Senior notes	194	197
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	337	337
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	$ 292	292
Senior Notes \| Series K Notes, interest rate of 3.0%, face amount of $600, maturing March 1, 2019 (effective interest rate of 4.4%)
Debt Instrument [Line Items]
Interest rate	3.00%
Senior notes, face amount	$ 600
Effective interest rate	4.40%
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 S Notes, interest rate of 6.8%, face amount of $324, maturing May 15, 2018 (effective interest rate of 1.7%)
Debt Instrument [Line Items]
Interest rate	6.80%
Senior notes, face amount	$ 324
Effective interest rate	1.70%
Senior Notes \| Series T Notes, interest rate of 7.2%, face amount of $181, maturing December 1, 2019 (effective interest rate of 2.3%)
Debt Instrument [Line Items]
Interest rate	7.20%
Senior notes, face amount	$ 181
Effective interest rate	2.30%
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%
Commercial paper
Debt Instrument [Line Items]
Commercial paper	$ 2,998	2,371
Other
Debt Instrument [Line Items]
Other	$ 267	$ 279

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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