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Earnings Per Share (Tables) | 6 Months Ended
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Jun. 30, 2012
Earnings Per Share [Abstract] |
Earnings per share |
|  | Three Months Ended June 30 |  |  | Six Months Ended June 30 |
|  | 2012 |  |  | 2011 |  |  | 2012 |  |  | 2011 |
Numerator (in millions): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income available to common stockholders |  | $ | 15.5 |  |  | $ | 24.6 |  |  | $ | 40.1 |  |  | $ | 46.1 |
Denominator (in thousands): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average common shares outstanding |  |  | 23,147 |  |  |  | 23,726 |  |  |  | 23,101 |  |  |  | 23,691 |
Dilutive effect of stock options and awards |  |  | 747 |  |  |  | 793 |  |  |  | 719 |  |  |  | 832 |
Denominator for diluted earnings per share |  |  | 23,894 |  |  |  | 24,519 |  |  |  | 23,820 |  |  |  | 24,523 |
Net income per share, basic |  | $ | 0.67 |  |  | $ | 1.04 |  |  | $ | 1.74 |  |  | $ | 1.95 |
Net income per share, diluted |  | $ | 0.65 |  |  | $ | 1.00 |  |  | $ | 1.68 |  |  | $ | 1.88 |

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- Definition Tabular disclosure of an entity's basic and diluted earnings per share calculations. + References No definition available. + Details
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