Stock-Based Compensation - Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-Based Compensation
Total stock-based compensation	$ 3.3	$ 3.1	$ 8.2	$ 8.4
Costs of product revenue
Stock-Based Compensation
Total stock-based compensation	0.5	0.5	1.2	1.3
Selling, general and administrative
Stock-Based Compensation
Total stock-based compensation	2.3	2.1	5.8	5.8
Research and development
Stock-Based Compensation
Total stock-based compensation	0.5	0.5	1.2	1.3
Stock options
Stock-Based Compensation
Total stock-based compensation	1.2	1.8	3.2	5.2
Restricted stock awards
Stock-Based Compensation
Total stock-based compensation	0.3	0.4	0.7	1.1
Restricted stock units
Stock-Based Compensation
Total stock-based compensation	$ 1.8	$ 0.9	$ 4.3	$ 2.1