Investments (Equity Method Investments) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Equity Method Investments [Line Items]
Foreign currency transactions losses (gains), net	$ (27.1)			$ (32.8)			$ (99.1)	$ (173.0)
Summarized results of operations of the VodafoneZiggo JV
Revenue	2,954.5			2,840.9			8,553.2	8,559.3
Loss before income taxes	(1,134.8)			516.4			(698.8)	(75.5)
Net loss	(973.6)	$ (503.8)	$ 1,017.7	12,885.1	$ 82.5	$ 15.7	(459.7)	12,983.3
All3Media
Schedule of Equity Method Investments [Line Items]
Foreign currency transactions losses (gains), net	(0.3)			(11.5)			(40.1)	(34.2)
VodafoneZiggo JV
Schedule of Equity Method Investments [Line Items]
Foreign currency transactions losses (gains), net	(6.8)			(21.8)			(34.9)	(124.1)
Formula E
Schedule of Equity Method Investments [Line Items]
Foreign currency transactions losses (gains), net	(17.4)			1.2			(16.7)	(8.7)
Other
Schedule of Equity Method Investments [Line Items]
Foreign currency transactions losses (gains), net	(2.6)			(0.7)			(7.4)	(6.0)
Equity Method Investment, Nonconsolidated Investee or Group of Investees | VodafoneZiggo JV
Summarized results of operations of the VodafoneZiggo JV
Revenue	1,166.7			1,096.9			3,345.4	3,275.3
Loss before income taxes	(31.6)			(83.7)			(58.5)	(407.0)
Net loss	$ (25.6)			$ (68.0)			$ (111.3)	$ (322.3)