Long-term Debt - Long-term Debt (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt, carrying amount	$ 8,898	$ 10,565
Commercial paper borrowings
Debt Instrument [Line Items]
Long-term debt, carrying amount	444	1,538
3.30% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,597	1,597
3.65% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,496	1,495
1.95% Senior Notes due 2016
Debt Instrument [Line Items]
Long-term debt, carrying amount	1,100	1,100
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
1.50% Guaranteed Notes due 2019
Debt Instrument [Line Items]
Long-term debt, carrying amount	561	628
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	$ 601	$ 608