Revenue and Capitalized Contract Costs - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized	$ 135.1	$ 92.1
Revenue expected to be recognized from remaining performance obligations for subscription contracts	$ 2,400.0
Capitalized contract cost, amortization period	5 years
Minimum | Subscriber Contracts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer, term	3 years
Maximum | Subscriber Contracts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer, term	5 years