Investments (Equity Method Investments) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net (note 5)	$ (29.2)			$ (27.1)			$ (35.6)	$ (99.1)
Revenue	1,901.4			2,845.4			8,390.5	8,233.7
Earnings (loss) before income taxes	317.8			(1,151.1)			13,333.4	(754.4)
Net earnings (loss)	318.7	$ 11,174.5	$ 1,440.3	(973.6)	$ (503.8)	$ 1,017.7	12,933.5	(459.7)
All3Media Group (All3Media)
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net (note 5)	(3.4)			(0.3)			(18.2)	(40.1)
VMED O2 JV
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net (note 5)	(10.4)			0.0			(10.7)	0.0
VMED O2 JV | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Revenue							4,822.5
Earnings (loss) before income taxes	56.3						(112.2)
Net earnings (loss)	31.9						(2.7)
VodafoneZiggo JV
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net (note 5)	(2.6)			(6.8)			6.8	(34.9)
VodafoneZiggo JV | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Revenue	1,206.1			1,166.7			3,638.4	3,345.4
Earnings (loss) before income taxes	(32.9)			(31.6)			(73.9)	(58.5)
Net earnings (loss)	(24.7)			(25.6)			(56.3)	(111.3)
Formula E Holdings Ltd (Formula E)
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net (note 5)	(10.9)			(17.4)			(6.5)	(16.7)
Other, net
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net (note 5)	$ (1.9)			$ (2.6)			$ (7.0)	$ (7.4)