Other Financial Statement Data (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Inventory [Line Items]
Demonstration inventory useful life (in months)			36 months
Accumulated amortization for demonstration inventories	$ 2,700,000		$ 2,700,000		$ 2,700,000
Amortization expense related to demonstration inventories	$ 175,000	$ 171,000	$ 498,000	$ 613,000
Minimum
Inventory [Line Items]
Product warranties time frame, years			1 year
Maximum
Inventory [Line Items]
Product warranties time frame, years			3 years