Basic and Diluted Earnings (Loss) Per Share (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Weighted-average basic shares outstanding	77,283,000	76,534,000	75,917,000
Effect of dilutive securities:
Weighted-average diluted shares outstanding	77,283,000	76,534,000	75,917,000
Basic earnings (loss) per share	$ (2.45)	$ (4.11)	$ (11.49)
Diluted earnings (loss) per share	$ (2.45)	$ (4.11)	$ (11.49)
Common share equivalents excluded from computation of diluted earnings (loss) per share	8,400,000	7,800,000	9,400,000

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

+ References

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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 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.

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+ Details