Segment Reporting (Geographic Segments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenue	$ 1,854.5	$ 1,746.3	$ 5,570.9	$ 5,353.8
VMO2 JV
Segment Reporting Information [Line Items]
Revenue	3,503.8	3,042.1	10,058.0	9,642.7
VodafoneZiggo JV
Segment Reporting Information [Line Items]
Revenue	1,125.2	1,041.7	3,297.0	3,237.3
Operating Segments | Switzerland
Segment Reporting Information [Line Items]
Revenue	859.3	789.8	2,482.9	2,377.3
Operating Segments | Belgium
Segment Reporting Information [Line Items]
Revenue	743.1	665.1	2,190.8	2,078.6
Operating Segments | Ireland
Segment Reporting Information [Line Items]
Revenue	125.5	116.1	372.4	365.4
Operating Segments | Slovakia
Segment Reporting Information [Line Items]
Revenue	12.8	12.0	39.2	37.3
Other, including intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	$ 113.8	$ 163.3	$ 485.6	$ 495.2