Revenues - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Deferred commission	$ 2.8	$ 2.7	$ 2.8	$ 2.7
Recognized service revenue	6.3	5.3	25.9	21.5
Refund liability	0.1	0.1	0.1	0.1
Prepaid expenses and other current assets
Disaggregation of Revenue [Line Items]
Deferred commission	1.9	1.8	1.9	1.8
Other long-term assets
Disaggregation of Revenue [Line Items]
Deferred commission	$ 0.9	$ 0.9	$ 0.9	$ 0.9