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Stock-Based Compensation (Additional Information) (Details)
3 Months Ended 6 Months Ended
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
offering_period
Jun. 30, 2014
USD ($)
Employee Stock Purchase Plan [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Compensation expense (income) $ 100,000 $ 100,000 $ 200,000 $ 200,000
Employee stock purchase plan, number of offering (offering period) | offering_period     2  
Employee stock purchase plan, offering period (months)     6 months  
Employee stock purchase plan, purchase price discount (percent)     15.00%  
Stock Options [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Stock options, contractual term (years)     10 years  
Stock-based compensation, approximate forfeitures rate (percent)     3.00%  
Compensation expense (income) 100,000 100,000 $ 100,000 200,000
Options exercised, total intrinsic value     6,400,000  
Total amount of cash received from exercise of options     $ 6,200,000  
Performance-Based Restricted Stock [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Stock-based compensation, approximate forfeitures rate (percent)     7.00%  
Compensation expense (income) $ 1,200,000 700,000 $ 1,600,000 $ 1,300,000
Restricted stock award program, measurement period (years)     3 years  
Expected dividend yield (percent)     0.00% 0.00%
Restricted stock award program, payment of award as percentage of target (percent) 120.00%   120.00%  
Performance-Based Restricted Stock [Member] | Minimum [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Restricted stock award program, awarded shares as a percentage of the original award amount (percent)     0.00%  
Performance-Based Restricted Stock [Member] | Maximum [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Restricted stock award program, awarded shares as a percentage of the original award amount (percent)     200.00%  
Time Based Restricted Stock [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Stock-based compensation, approximate forfeitures rate (percent)     7.00%  
Compensation expense (income) $ 1,300,000 1,100,000 $ 2,400,000 $ 2,100,000
Time Based Restricted Stock [Member] | 2011 Grants [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Restricted stock award program, vesting period (years)     4 years  
Time Based Restricted Stock [Member] | 2012 Grants [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Restricted stock award program, vesting period (years)     3 years  
Deferred Stock Units [Member]        
Compensation Related Costs Share Based Payments Disclosure [Line Items]        
Compensation expense (income) $ 0 $ 0 $ 700,000 $ 800,000