Revenue from Contracts with Customers - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) numberOfSources	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Sources of revenue | numberOfSources			3
Deferred revenue	$ 12,872	$ 10,023	$ 12,872	$ 10,023	$ 12,872	$ 10,023	$ 11,537	$ 10,498	$ 10,980	$ 11,176
Amortization of capitalized commission costs	1,046	613	2,728	1,750
Hardware and other
Disaggregation of Revenue [Line Items]
Reserve for hardware returns					1.00%	1.00%
Commissions and upfront payments made to a customer
Disaggregation of Revenue [Line Items]
Amortization of capitalized commission costs	1,000	$ 600	2,700	$ 1,800
Activation Fees
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 7,200		$ 7,200		$ 7,200			$ 8,100