Segment Reporting (Performance Measures) (Schedule) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 1,901.4	$ 2,845.4	$ 8,390.5	$ 8,233.7
Adjusted EBITDA	758.5	1,163.5	3,273.2	3,406.1
VMED O2 JV | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Segment Reporting Information [Line Items]
Revenue			4,822.5
VodafoneZiggo JV | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Segment Reporting Information [Line Items]
Revenue	1,206.1	1,166.7	3,638.4	3,345.4
Adjusted EBITDA	578.1	559.1	1,713.4	1,593.4
VMED O2 JV (U.K.) | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Segment Reporting Information [Line Items]
Revenue	3,614.0	0.0	4,822.5	0.0
Adjusted EBITDA	1,180.3	0.0	1,591.3	0.0
Operating Segments | U.K.
Segment Reporting Information [Line Items]
Revenue	0.0	1,543.6	2,736.4	4,457.3
Adjusted EBITDA	0.0	610.9	1,085.3	1,819.6
Operating Segments | Belgium
Segment Reporting Information [Line Items]
Revenue	755.4	746.6	2,302.9	2,147.2
Adjusted EBITDA	369.1	367.4	1,130.5	1,053.1
Operating Segments | Switzerland
Segment Reporting Information [Line Items]
Revenue	830.2	315.0	2,497.4	930.9
Adjusted EBITDA	330.8	154.4	910.9	439.4
Operating Segments | Ireland
Segment Reporting Information [Line Items]
Revenue	136.0	126.4	406.2	366.2
Adjusted EBITDA	59.1	49.9	160.7	143.2
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Revenue	181.4	118.9	458.7	346.9
Adjusted EBITDA	1.5	(20.5)	(15.8)	(50.6)
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	(1.6)	(5.1)	(11.1)	(14.8)
Intersegment eliminations	$ (2.0)	$ 1.4	$ 1.6	$ 1.4