Capitalized Contract Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Costs of fulfill a contract - amortization expense	$ 5.7	$ 5.5	$ 11.9	$ 10.7
Cost to fulfill contract, net	80.0		80.0		$ 79.5
Deferred Commissions
Capitalized Contract Cost [Line Items]
Deferred commissions	11.8		11.8		$ 12.1
Costs of fulfill a contract - amortization expense	$ 1.0	$ 1.7	$ 2.0	$ 3.4