Stock-Based Compensation - Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stock-Based Compensation
Total stock-based compensation	$ 2.7	$ 2.5
Costs of product revenue
Stock-Based Compensation
Total stock-based compensation	0.4	0.4
Selling, general and administrative
Stock-Based Compensation
Total stock-based compensation	1.9	1.7
Research and development
Stock-Based Compensation
Total stock-based compensation	0.4	0.4
Mestrelab Research, S.L
Stock-Based Compensation
Total stock-based compensation	0.4
Stock options
Stock-Based Compensation
Total stock-based compensation	0.7	1.0
Restricted stock awards
Stock-Based Compensation
Total stock-based compensation	0.1	0.2
Restricted stock units
Stock-Based Compensation
Total stock-based compensation	$ 1.9	$ 1.3