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Shareholders’ equity (Tables) | 3 Months Ended
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Mar. 31, 2014
Stockholders' Equity Note [Abstract] |
Common and Preferred Stock Activity | See Common and Preferred Stock Activity table below for additional information about preferred stock conversions during the period.
Common and Preferred Stock Activity: | Preferred stock |  | Common stock
(in shares) | Series A convertible |  | Treasury | Outstanding
Beginning balance as of December 31, 2013 | 79,620 |  |  | 4,786,521 |  | 88,710,277 |
Conversion of convertible preferred stock | (255 | ) |  | — |  | 25,542 |
Issuance for share-based compensation plans | — |  |  | — |  | 35,624 |
Ending balance as of March 31, 2014 | 79,365 |  |  | 4,786,521 |  | 88,771,443 |
Beginning balance as of December 31, 2012 | 80,283 |  |  | 4,786,521 |  | 88,548,637 |
Conversion of convertible preferred stock | (199 | ) |  | — |  | 19,864 |
Issuance for share-based compensation plans | — |  |  | — |  | 27,708 |
Ending balance as of March 31, 2013 | 80,084 |  |  | 4,786,521 |  | 88,596,209 |

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- Definition Tabular disclosure of the change in preferred stock, treasury stock and common stock outstanding. + References No definition available. + Details
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