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Stock-Based Compensation Stock-Based Compensation Narrative (Details) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Stock Incentive Plan [Member]
   
[Line Items]    
Number of shares authorized for issuance under the share based compensation plan 3,500,000  
Number of shares available for future grant under the Stock Incentive Plan 509,259  
Stock Option or Share Appreciation Right [Member]
   
[Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Fungible Share Provision 1  
Awards Other than Stock Options or Share Appreciation Rights [Member]
   
[Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Fungible Share Provision 1.7  
Employee Stock Option [Member]
   
[Line Items]    
Award vesting rights Options generally become exercisable in three equal annual installments beginning one year from the date of grant  
Unrecognized compensation expense 4.7  
Unrecognized compensation expense, Expected weighted average period for recognition (years) 2 years 6 months 20 days  
Stock options expiration period (years) 10 years  
Restricted Stock Units (RSUs) [Member]
   
[Line Items]    
Unrecognized compensation expense 30.3  
Unrecognized compensation expense, Expected weighted average period for recognition (years) 2 years 1 month 3 days  
Award vesting period 3 years  
Long Term Performance Restricted Stock Award [Member]
   
[Line Items]    
Restricted Awards Eligible for Vesting   0
Performance Condition Vesting Range, Lower Range Limit 0.00%  
Performance Condition Vesting Range, Upper Range Limit 160.00%  
Market Condition Multiplier, Lower Range Limit 75.00%  
Market Condition Multiplier, Upper Range Limit 125.00%  
Possible Total Percentage of Shares Vested, Lower Range Limit 0.00%  
Possible Total Percentage of Shares Vested, Upper Range Limit 200.00%  
Employee Stock [Member]
   
[Line Items]    
ESPP, percentage discount from market price on purchase date 15.00%  
ESPP, maximum percentage of employee salary eligible for participation 10.00%  
Shares available for future issuance under the ESPP 580,000