Long-term Debt - Long-term Debt (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 11,626	$ 10,393
3.30% Senior Notes due 2021
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,596	1,596
3.65% Senior Notes due 2023
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,495	1,495
2.75% Guaranteed Notes due 2015
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,273	1,373
1.95% Senior Notes due 2016
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,099	1,099
4.20% Senior Notes due 2021
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,100	1,099
1.25% Senior Notes due 2017
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,000	999
2.40% Senior Notes due 2022
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	999	999
1.50% Guaranteed Notes due 2019
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	656	697
2.65% Senior Notes due 2016
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	500	500
Commercial Paper Borrowings
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	1,392
Other
Proforma Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 516	$ 536