Calculation Of Net Income Per Share (Weighted-Average Shares Used In Calculation Of Basic And Diluted EPS) (Details) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share [Abstract]
Weighted-average number of common shares outstanding	159,344	170,193
Stock options	201	445
Unvested restricted stock units	767	814
Conversion spread related to Convertible Debentures	2,541	506
Employee stock purchase plan	28	21
Shares used to compute diluted net income per share	162,881	171,979

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of equity unit purchase agreements using the treasury stock method.

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Nonvested equity-based payment awards that contain forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) that result in incremental common shares.

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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

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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