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Earnings per common 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
Earnings per common share [Abstract]
Weighted average common shares outstanding - basic	188,831	188,794	188,824	188,753
Effect of dilutive stock options and performance share awards	0	3	205	7
Weighted average common shares outstanding - diluted	188,831	188,797	189,029	188,760
Shares excluded from the calculation of diluted earnings per share	434	0	0	0

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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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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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