Revenue (Summary of Revenue by Category) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Product Information [Line Items]
Total revenue	$ 21,915	$ 18,160	$ 62,961	$ 59,100
Product [Member]
Product Information [Line Items]
Total revenue	18,484	15,150	53,191	49,917
Instrument [Member]
Product Information [Line Items]
Total revenue	11,583	6,296	29,870	21,965
Consumable [Member]
Product Information [Line Items]
Total revenue	6,901	8,854	23,321	27,952
Service and Other [Member]
Product Information [Line Items]
Total revenue	$ 3,431	$ 3,010	$ 9,770	$ 9,183