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Share-Based Compensation - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total intrinsic value of options exercised during period $ 7.4 $ 2.8 $ 2.7
Cash received from options exercised during period 2.8 $ 1.3 $ 1.5
Unrecognized pre-tax compensation cost $ 2.4    
Weighted average recognition period (in years) 2 years 20 days    
Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options, exercisable period 2 years    
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options, exercisable period 10 years    
All Other Options Granted [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Annual vesting, percentage 20.00%    
Director [Member] | Options Granted Prior to May 25, 2004 [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options, exercisable period 9 years    
Vesting period 1 year    
Director [Member] | Options Granted on or after May 25, 2004 [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Annual vesting, percentage 33.33%    
1992 Stock Option Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock authorized to be issued under plan (in shares) 14,900,000.0    
Exercise price of shares granted may not be less than fair market value (percentage) 85.00%    
2007 Long-Term Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock authorized to be issued under plan (in shares) 3,300,000.0    
Exercise price of shares granted may not be less than fair market value (percentage) 100.00%    
Vesting term Since inception of the LTIP, non-qualified stock options and restricted stock awards have been granted with the same vesting schedule as the previous plan.      
Restricted Stock [Member] | Director [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Annual vesting, percentage 33.33%    
Restricted Stock [Member] | 2007 Long-Term Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Annual vesting, percentage 20.00%    
Unrecognized pre-tax compensation cost $ 4.7    
Weighted average recognition period (in years) 1 year 11 months 28 days