| **Earnings per share**            | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
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| **Earnings Per Share [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Earnings Per Share                | EARNINGS PER SHAREBasic earnings per share is computed by dividing net earnings by the weighted-average number of common shares outstanding for the period. Diluted earnings per share is similarly computed except that the denominator includes the effect, using the treasury stock method, of unvested restricted stock, outstanding SARs, stock options, Convertible Notes and shares held pursuant to our non-employee director deferred compensation plan, if including such potential shares of common stock is dilutive.The following table presents a reconciliation of the weighted-average diluted shares outstanding: Three Months Ended September 30, Nine Months Ended September 30, 2013 2012 2013 2012 (in thousands)        Weighted-average common shares outstanding - basic33,413 30,214 31,350 26,819Weighted-average common shares and equivalents outstanding - diluted33,413 30,214 31,350 26,819        We reported a net loss for each of the three and nine months ended September 30, 2013, and 2012, respectively. As a result, our basic and diluted weighted-average common shares outstanding was the same as the effect of the common share equivalents was anti-dilutive.The following table presents the weighted-average common share equivalents excluded from the calculation of diluted earnings per share due to their anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2013 2012 2013 2012 (in thousands)        Weighted-average common share equivalents excluded from diluted earnings       per share due to their anti-dilutive effect:       Restricted stock805 777 857 688SARs83 119 65 115Stock options7 7 7 7Non-employee director deferred compensation4 3 4 3Convertible senior notes671 — 387 —Total anti-dilutive common share equivalents1,570 906 1,320 813        In November 2010, we issued our Convertible Notes, which give the holders the right to convert the aggregate principal amount into 2.7 million shares of our common stock at a conversion price of $42.40 per share. The Convertible Notes could be included in the dilutive earnings per share calculation using the treasury stock method if the average market share price exceeds the $42.40 conversion price during the period presented. Shares issuable upon conversion of the Convertible Notes were excluded from the diluted earnings per share calculation for the three and nine months ended September 30, 2013 as the effect would be anti-dilutive to our earnings per share. Shares issuable upon conversion of the Convertible Notes were excluded from the diluted earnings per share calculation for the three and nine months ended September 30, 2012 as the conversion price was greater than the average market price of our common stock during the period. |

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| - Definition
The entire disclosure for earnings per share.
+ References
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