Net Income Per Share (Computation Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net Income Per Share
Net income	$ 68,214	$ 43,519	$ 128,447	$ 75,791
Weighted-average common shares outstanding	52,470	52,486	52,614	52,697
Basic earnings per share	$ 1.30	$ 0.83	$ 2.44	$ 1.44
Employee stock options and employee stock purchase plan shares	1,439	1,838	1,463	1,851
Weighted-average number of shares	53,909	54,324	54,077	54,548
Diluted earnings per share	$ 1.26	$ 0.80	$ 2.37	$ 1.39

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=6519514

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Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=6518256

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-Name Regulation S-X (SX)
-Number 210
-Article 5
-Section 03
-Paragraph 19

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
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+ 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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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Glossary Weighted-Average Number of Common Shares Outstanding
-URI http://asc.fasb.org/extlink&oid=6528421

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+ Details