Common Share Data Used for Computing Basic and Diluted Earnings Per Share (Detail) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Common share data used for computing the basic and diluted earnings per share
Number of common shares outstanding at end of period	463.9	461.2	463.9	461.2
Effect of using weighted average common shares outstanding	0.2	7.1	(0.6)	11.5
Weighted average basic common shares outstanding	464.1	468.3	463.3	472.7
Dilutive effect of equity-based compensation awards and other contingently issuable shares	0.8	1.4	0.9	1.8
Weighted average diluted common shares outstanding	464.9	469.7	464.2	474.5
Potentially issuable shares	16.5	17.3	16.5	17.3
Number of anti-dilutive potentially issuable shares excluded from diluted common shares outstanding	8.1	9.9	8.1	6.4

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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-Publisher FASB

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-Number 07-4

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Diluted Earnings Per Share

-URI http://asc.fasb.org/extlink&oid=6510752

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Contingent Stock Agreement

-URI http://asc.fasb.org/extlink&oid=6508534

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-Name Accounting Standards Codification

-Glossary Antidilution

-URI http://asc.fasb.org/extlink&oid=6505113

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 40

-Subparagraph c

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-Topic 260

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+ Details

- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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- Definition

This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

+ References

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+ Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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-Publisher FASB

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-Publisher FASB

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Weighted-Average Number of Common Shares Outstanding

-URI http://asc.fasb.org/extlink&oid=6528421

+ Details