Segment Reporting (Performance Measures) (Schedule) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 2,954.5	$ 2,840.9	$ 8,553.2	$ 8,559.3
VodafoneZiggo JV
Segment Reporting Information [Line Items]
Adjusted EBITDA	559.1	500.1	1,593.4	1,481.5
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	1,209.2	1,211.7	3,548.0	3,585.7
Operating Segments | U.K./Ireland
Segment Reporting Information [Line Items]
Revenue	1,669.5	1,579.9	4,821.9	4,885.2
Adjusted EBITDA	665.0	657.8	1,975.3	2,037.5
Operating Segments | Belgium
Segment Reporting Information [Line Items]
Revenue	746.6	721.9	2,147.2	2,147.0
Adjusted EBITDA	367.4	358.6	1,053.1	1,047.0
Operating Segments | Switzerland
Segment Reporting Information [Line Items]
Revenue	315.0	311.7	930.9	942.7
Adjusted EBITDA	154.4	160.2	439.4	476.3
Operating Segments | Central and Eastern Europe
Segment Reporting Information [Line Items]
Revenue	124.2	117.2	359.5	355.4
Adjusted EBITDA	54.0	54.6	161.0	162.4
Central and Corporate | Central and Corporate
Segment Reporting Information [Line Items]
Revenue	101.9	110.5	296.8	231.4
Adjusted EBITDA	(31.6)	(19.2)	(80.8)	(138.6)
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	(2.7)	(0.3)	(3.1)	(2.4)
Adjusted EBITDA	0.0	(0.3)	0.0	1.1
Equity Method Investment, Nonconsolidated Investee or Group of Investees | VodafoneZiggo JV
Segment Reporting Information [Line Items]
Revenue	$ 1,166.7	$ 1,096.9	$ 3,345.4	$ 3,275.3