| Earnings Per Share | 9 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Sep. 30, 2011 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Earnings Per Share [Abstract] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Earnings Per Share | 
12. Earnings Per Share
    Basic earnings per share represents net income for the period common shares were outstanding,
   divided by the weighted average number of common shares outstanding for the period. Diluted
   earnings per share represents net income divided by the weighted average number of common shares
   outstanding, inclusive of the effect of dilutive securities such as outstanding stock options,
   SARs, stock units and warrants.
    The following are the common share amounts used to compute the basic and diluted earnings per
   share for each period:
    
 There were an aggregate of 2.0 million and 2.1 million of equity grants that were outstanding
   during the three and nine months ended September 30, 2011, and
   an aggregate of 1.6 million and 3.4
   million of equity grants that were outstanding during the three and nine months ended September 30,
   2010, respectively, consisting of stock options, SARs, and stock units, but were not included in
   the computation of diluted earnings per share because their effect would be anti-dilutive.
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