Inventories - Narrative (Details)	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Line Items]
Demonstration inventory shelf life (in years)	3 years
Refurbished demonstration inventory selling period (in months)	12 months
Service Inventory
Property, Plant and Equipment [Line Items]
Service inventory selling period (in months)	12 months
Inventory, remaining useful life (in years)	3 years