Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Summary of Long-Term Debt
Long-term debt, carrying amount	$ 8,439		$ 8,548
Fair value adjustment-hedging			8
Other Long-term Debt, Noncurrent, Total	8,439		8,556
Other variable rate debt [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	272	[1]	271
3.300% Senior Notes due 2021 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	1,595		1,595
4.50% Guaranteed Notes due 2014 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	1,343		1,290
2.75% Guaranteed Notes due 2015 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	1,336		1,297
1.950% Senior Notes due 2016 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	1,099		1,099
4.200% Guaranteed Notes due 2021 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	1,099		1,099
5.25% Guaranteed Notes due 2013 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	671		649
2.650% Senior Notes due 2016 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	498		498
3.00% Guaranteed Notes due 2013 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount			450
Floating Rate Senior Notes due 2014 [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	300		300
Commercial Paper Borrowing [Member]
Summary of Long-Term Debt
Long-term debt, carrying amount	$ 226

[1] Net of the effect of business acquisitions and divestitures.