Other Financial Statement Data (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 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
Amortization expense related to demonstration inventories	$ 154,000	$ 230,000
Minimum
Inventory [Line Items]
Product warranties time frame, years	1 year
Maximum
Inventory [Line Items]
Product warranties time frame, years	3 years