Description of Business and Significant Accounting Policies - Revenue Recognition (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Description Of Business And Significant Accounting Policies [Line Items]
Unbilled receivables, current	$ 2,300,000		$ 2,300,000		$ 2,000,000.0
Deferred commissions balance, beginning of period	16,965,000	$ 17,365,000	17,902,000	$ 17,331,000	17,331,000
Deferral of commissions earned	4,784,000	4,535,000	8,448,000	8,591,000
Recognition of commission expense	(4,978,000)	(4,048,000)	(9,574,000)	(7,977,000)
Impairment of deferred commissions	(35,000)	(125,000)	(40,000)	(218,000)
Deferred commissions balance, end of period	16,736,000	$ 17,727,000	16,736,000	$ 17,727,000	17,902,000
Other assets
Description Of Business And Significant Accounting Policies [Line Items]
Unbilled receivables, noncurrent	808,000		808,000		795,000
Unbilled
Description Of Business And Significant Accounting Policies [Line Items]
Accounts receivable	$ 2,298,000		$ 2,298,000		$ 2,043,000
Minimum
Description Of Business And Significant Accounting Policies [Line Items]
Payment terms			30 days
Maximum
Description Of Business And Significant Accounting Policies [Line Items]
Payment terms			60 days
Total revenue | Product | Appliance | Maximum
Description Of Business And Significant Accounting Policies [Line Items]
Concentration risk, percentage			1.00%