Outstanding Debentures (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Debt Instrument [Line Items]
Outstanding principal amount	$ 5,814
Exchangeable 2009 Senior Debentures 2.5 Percent Due October 2029
Debt Instrument [Line Items]
Maturity date	Oct. 15, 2029
Next put option date	Oct. 15, 2015
Redemption date	Oct. 20, 2015
Outstanding principal amount	400
Current exchange rate for each $1,000 of principal	71.9264
Current equivalent exchange price	$ 13.90
Exchangeable share equivalents (in shares)	28.8
Exchangeable 2007 Senior Debentures 2.625 Percent Due April 2027
Debt Instrument [Line Items]
Maturity date	Apr. 15, 2027
Next put option date	Apr. 15, 2012
Redemption date	Apr. 20, 2012
Outstanding principal amount	388
Current exchange rate for each $1,000 of principal	32.0239
Current equivalent exchange price	$ 31.23
Exchangeable share equivalents (in shares)	12.4
Exchangeable 2004 Senior Debentures 3.25 Percent Due April 2024
Debt Instrument [Line Items]
Maturity date	Apr. 15, 2024
Next put option date	Apr. 15, 2014
Redemption date	Apr. 19, 2009
Outstanding principal amount	175
Current exchange rate for each $1,000 of principal	65.5744
Current equivalent exchange price	$ 15.25
Exchangeable share equivalents (in shares)	11.5
Exchangeable Debentures
Debt Instrument [Line Items]
Outstanding principal amount	$ 963

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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The ratio applied to the debt for purposes of determining the number of shares of the equity security into which the debt will be converted.

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- Definition

The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details