Reconciliation of Share Amount Used in Computation of Basic and Diluted Earnings Per Share (Detail) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Basic earnings (loss) per share-Weighted common shares outstanding	137,306	134,685	131,685
Weighted common shares assumed upon exercise of options and vesting of restricted stock units	1,106	1,538	1,489
Diluted earnings (loss) per share-Weighted common shares outstanding	138,412	136,223	133,174

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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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

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.

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

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

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-Name Emerging Issues Task Force (EITF)

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

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

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