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Revenue Related Disclosures - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Jan. 01, 2018
Disaggregation Of Revenue [Line Items]
Deferred revenue		$ 18.5		$ 18.5
Deferred revenue added from new billings	$ 8.1	12.1	$ 26.8	27.9
United States
Disaggregation Of Revenue [Line Items]
Revenues	9.8	9.0	28.9	24.3
South Africa
Disaggregation Of Revenue [Line Items]
Revenues	0.2	0.2	0.9	0.7
Bahamas
Disaggregation Of Revenue [Line Items]
Revenues	0.2		0.9
Adoption of Topic 606
Disaggregation Of Revenue [Line Items]
Deferred revenue					$ 24.2	$ 17.3
Recognition from Beginning Deferred Revenue Balance
Disaggregation Of Revenue [Line Items]
Deferred revenue recognized	8.8	5.9	20.0	13.9
Recognition from New Billings of Deferred Revenue
Disaggregation Of Revenue [Line Items]
Deferred revenue recognized	$ 1.1	$ 3.1	$ 9.7	$ 10.8