Goodwill and Other Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	[1]	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, Beginning Balance					$ 2,128.0	$ 2,079.7	$ 2,128.0
Currency translation adjustments						3.4	(5.4)
Impairment charge	$ 0.0	$ 0.0	$ (42.9)		0.0	0.0	(42.9)	$ 0.0
Goodwill, Ending Balance	2,079.7					2,083.1	2,079.7	2,128.0
U.S. Media
Goodwill [Roll Forward]
Goodwill, Beginning Balance					2,054.0	2,054.0	2,054.0
Currency translation adjustments						0.0	0.0
Impairment charge							0.0
Goodwill, Ending Balance	2,054.0					2,054.0	2,054.0	2,054.0
Other
Goodwill [Roll Forward]
Goodwill, Beginning Balance					$ 74.0	25.7	74.0
Currency translation adjustments						3.4	(5.4)
Impairment charge							(42.9)
Goodwill, Ending Balance	$ 25.7					$ 29.1	$ 25.7	$ 74.0

[1] As a result of an impairment analysis performed during the second quarter of 2018, we determined that the carrying value of our Canadian reporting unit exceeded its fair value and we recorded an impairment charge of $42.9 million on the Consolidated Statement of Operations. See Note 6. Goodwill and Other Intangible Assets: Goodwill to the Consolidated Financial Statements