Shareholders' Equity - Reconciliation of Weighted Average Number of Shares (Detail) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Weighted Average Number of Shares Outstanding [Line Items]
Weighted average number of common shares outstanding	68,910	68,261	68,600	68,315
Director Plan and deferred stock units	196	332	257	343
ESOP	73	99	89	103
Common shares outstanding—basic	69,179	68,692	68,946	68,761
Common and potential common shares outstanding—diluted	71,186	70,883	70,901	70,956
Option plans and Omnibus Plan
Weighted Average Number of Shares Outstanding [Line Items]
Dilutive effect of Option Plans and Omnibus Plan	2,007	2,191	1,955	2,195

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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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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- 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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-Glossary Weighted-Average Number of Common Shares Outstanding

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

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