Goodwill and Other Intangible Assets - Schedule of Goodwill and Other Intangible Assets Footnotes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Foreign currency translation		$ 0.0		$ 0.0
Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Foreign currency translation	$ (1.6)	$ (1.2)	$ (1.6)	$ (1.2)
NSM Holding Co LLC | Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Foreign currency translation					$ (0.7)
NSM Holding Co LLC | Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Foreign currency translation	$ (1.5)				(2.2)
Buzzmove | Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Foreign currency translation			$ (0.1)		$ (0.3)