Debt and Credit Facility - Additional Information (Detail) (USD $)	Mar. 31, 2012	Mar. 30, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Debt financing program through the issuance of commercial paper	$ 3,000,000,000
Amounts of commercial paper outstanding	2,000,000,000		750,000,000
Weighted average yield for commercial paper outstanding	0.10%		0.10%
Short-term debt	2,468,000,000		1,218,000,000
Estimated fair value of long-term debt		3,100,000,000
Revolving credit facility	3,000,000,000
Revolving credit facility, amount outstanding	0		0
Promissory Notes
Line of Credit Facility [Line Items]
Short-term debt	468,000,000		468,000,000
Secured promissory note, interest rate	1.00%
Secured promissory note, maturity date	2012-12
Debt instrument, face amount	468,000,000
Unsecured Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, face amount			$ 3,000,000,000
Number of unsecured senior notes tranches			3
1.25% Notes due on May 19, 2014
Line of Credit Facility [Line Items]
Secured promissory note, interest rate	1.25%
Effective interest rate	1.258%
2.125% Notes due on May 19, 2016
Line of Credit Facility [Line Items]
Secured promissory note, interest rate	2.125%
Effective interest rate	2.241%
3.625% Notes due on May 19, 2021
Line of Credit Facility [Line Items]
Secured promissory note, interest rate	3.625%
Effective interest rate	3.734%