Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation and Employee Benefit Plans (Details 5)

v2.4.0.6
Share-Based Compensation and Employee Benefit Plans (Details 5) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Performance share units
     
Share-Based Compensation      
Estimated pre-vesting forfeitures (as a percent) 0.00% 0.00%  
Unrecognized compensation cost 2.9    
Expected weighted average period during which unrecognized compensation cost will be recognized (in years) 2    
Restricted shares
     
Share-Based Compensation      
Unrecognized compensation cost 12.5    
Expected weighted average period during which unrecognized compensation cost will be recognized (in years) 2    
Restricted shares | Minimum
     
Share-Based Compensation      
Estimated pre-vesting forfeitures (as a percent) 0.00% 0.00% 2.00%
Restricted shares | Maximum
     
Share-Based Compensation      
Estimated pre-vesting forfeitures (as a percent) 4.00% 4.00% 5.00%
Options
     
Share-Based Compensation      
Estimated pre-vesting forfeitures (as a percent)     0.00%