Long-term Debt and Debt Facility Agreements - Long-term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 14,442	$ 10,565
Commercial paper borrowings
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,000	1,538
4.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,741
3.30% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,597	1,597
3.00% Senior Notes due 2020
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,591
3.65% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,496	1,495
2.35% Senior Notes due 2018
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,297
4.20% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,100	1,100
1.25% Senior Notes due 2017
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,000	1,000
2.40% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	999	999
3.63% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, carrying amount	845
1.50% Guaranteed Notes due 2019
Debt Instrument [Line Items]
Long-term debt, carrying amount	566	628
1.90% Senior Notes due 2017
Debt Instrument [Line Items]
Long-term debt, carrying amount	499
1.95% Senior Notes due 2016
Debt Instrument [Line Items]
Long-term debt, carrying amount		1,100
2.65% Senior Notes due 2016
Debt Instrument [Line Items]
Long-term debt, carrying amount		500
Other
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 711	$ 608