Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Narrative) (Details)

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Stockholders' Equity (Narrative) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Corporate Share Repurchase    
Stock repurchase, authorized amount $ 5.0  
Stock repurchase, maximum period 1 year  
Stock Options
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Rights 1/8 on the six month anniversary of the date of grant, and 1/48 each month thereafter for 42 months  
Award Expiration Period 10 years  
Weighted-average grant date fair value of stock options $ 47.93  
Intrinsic value of options exercised 12.1 0.2
Unrecognized compensation cost 17.9  
Weighted-average period in which cost is expected to be recognized 2 years 6 months 15 days  
Restricted Stock
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted-average period in which cost is expected to be recognized 1 year 5 months 27 days  
Unrecognized compensation cost, restricted stock 2.6  
2002 Stock Incentive Plan | Stock Options
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares available for future option grants 1,100,000  
Employee Stock Purchase Plan
   
Employee Stock Purchase Plan    
Shares allowed to purchase in employee stock purchase plan 1,250  
Offering period of shares in employee stock purchase plan 6 months  
Percentage of purchase price of stock 85.00%  
Discount rate 15.00%  
Shares available for future purchases 79,515  
Employee Stock Purchase Plan | Stock Options
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Net proceeds from employee stock purchase plan $ 3.2 $ 0.3
Certain Directors | 2002 Stock Incentive Plan
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 1 year  
Employees
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 4 years  
Vesting Period One | 2002 Stock Incentive Plan | Stock Options
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 6 months  
Award Vesting Rights, Percentage 12.50%  
Vesting Period Two | 2002 Stock Incentive Plan | Stock Options
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award Vesting Period 42 months  
Award Vesting Rights, Percentage 2.08%