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Summary of Significant Accounting Policies - Stock-Based Compensation (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Stock-Based Compensation      
Total stock-based compensation $ 11.3 $ 11.0 $ 9.4
Estimated forfeiture rate (as a percent) 7.50% 6.70% 6.20%
Costs of product revenue      
Stock-Based Compensation      
Total stock-based compensation $ 1.7 $ 1.7 $ 1.4
Selling, general and administrative      
Stock-Based Compensation      
Total stock-based compensation 7.9 7.6 6.6
Research and development      
Stock-Based Compensation      
Total stock-based compensation 1.7 1.7 1.4
Stock options      
Stock-Based Compensation      
Total stock-based compensation $ 4.2 $ 6.2 $ 7.5
Risk-free interest rates, minimum (as a percent) 2.80% 1.78% 1.23%
Risk-free interest rates, maximum (as a percent)   2.09% 2.21%
Expected life 5 years 4 months 17 days 5 years 6 months 22 days  
Volatility (as a percent) 28.46%    
Volatility, minimum (as a percent)   30.78% 33.57%
Volatility, maximum (as a percent)   34.13% 41.60%
Expected dividend yield (as a percent) 0.47%    
Stock options | Minimum      
Stock-Based Compensation      
Vesting period 3 years    
Expected life     5 years 9 months
Expected dividend yield (as a percent)   0.55% 0.00%
Stock options | Maximum      
Stock-Based Compensation      
Vesting period 4 years    
Expected life     7 years 7 days
Expected dividend yield (as a percent)   0.74% 0.78%
Restricted stock awards      
Stock-Based Compensation      
Total stock-based compensation $ 0.8 $ 1.4 $ 1.6
Restricted stock units      
Stock-Based Compensation      
Total stock-based compensation $ 6.3 $ 3.4 $ 0.3