Reconciliation of Basic to Diluted Shares Outstanding (Detail) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Weighted Average Number of Diluted Shares Outstanding [Line Items]
Basic	223.2	226.3	235.0
Dilutive effect of shares issuable under stock-based compensation plans	3.4	3.1	1.6
Diluted	226.6	229.4	236.6
Antidilutive options to purchase common shares and restricted stock as well as contingently issuable restricted stock which are excluded from the table above	7.5	10.6	15.5

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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+ Details

- Definition

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

+ References+ Details

- 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.

+ References+ 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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+ Details