Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 11,537	$ 10,980	$ 11,537	$ 10,980	$ 11,537	$ 10,980	$ 12,102	$ 10,498	$ 11,536	$ 11,176
Amortization of capitalized commission costs	871	623	1,682	1,137
Hardware and other revenue
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	900	$ 600	1,700	$ 1,100
Activation Fees
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 7,500		$ 7,500		$ 7,500			$ 8,100