Capitalized Contract Costs (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
Capitalized Contract Cost [Line Items]
Costs to fulfill a contract - amortization expense	$ 5.9	$ 4.2	$ 17.8	$ 14.9
Cost to fulfill contract, net	78.1		78.1		$ 79.5
Deferred Commissions
Capitalized Contract Cost [Line Items]
Deferred commissions	11.2		11.2		$ 12.1
Costs to fulfill a contract - amortization expense	$ 0.9	$ 1.8	$ 2.9	$ 5.2