Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Estimated amortization expense of intangible assets for 2019		$ 34.3
Estimated amortization expense of intangible assets for 2020		33.1
Estimated amortization expense of intangible assets for 2021		30.7
Estimated amortization expense of intangible assets for 2022		27.6
Estimated amortization expense of intangible assets for 2023		22.6
Estimated amortization expense of intangible assets for later years		173.4
Impairment charge	$ 29.4
Impairment of intangible assets	$ 6.3
Cable And Satellite Carriage Rights
Goodwill [Line Items]
Intangible software assets acquired		$ 5.8	$ 9.7