Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Deferred contract costs and capitalized sales commissions
Capitalized Contract Cost [Line Items]
Capitalized contract cost, gross	$ 87.0		$ 89.2
Capitalized sales commissions to selling, general and administrative expenses
Capitalized Contract Cost [Line Items]
Capitalized contract cost, amortization	3.0	$ 2.6
Other deferred contract costs as a reduction of revenue
Capitalized Contract Cost [Line Items]
Capitalized contract cost, amortization	$ 1.5	$ 1.4