Earnings per share (Details) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Weighted Average Number of Shares Outstanding Reconciliation
Weighted average number of common shares outstanding used to compute basic earnings per share	52,131	37,001	44,777	36,866
Dilutive effect of stock-based awards	1,031	768	1,030	890
Number of shares used to compute diluted earnings per share	53,162	37,769	45,807	37,756
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive common share equivalents outstanding	170	1,385	49	1,059

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 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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+ Details