Segment Reporting (Performance Measures) (Schedule) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 2,850.4	$ 3,015.6	$ 5,718.4	$ 6,079.1
Adjusted OIBDA	1,190.7	1,303.5	2,374.0	2,565.2
VodafoneZiggo JV
Segment Reporting Information [Line Items]
Revenue	1,084.5	1,133.3	2,178.4	2,329.9
Adjusted OIBDA	487.6	502.8	981.4	1,019.7
Operating Segments
Segment Reporting Information [Line Items]
Adjusted OIBDA	1,190.7	1,303.5	2,374.0	2,565.2
Operating Segments | U.K./Ireland
Segment Reporting Information [Line Items]
Revenue	1,644.0	1,734.9	3,305.3	3,513.1
Adjusted OIBDA	703.2	763.6	1,411.5	1,526.2
Operating Segments | Belgium
Segment Reporting Information [Line Items]
Revenue	713.2	753.9	1,425.1	1,513.5
Adjusted OIBDA	349.4	383.7	688.4	741.3
Operating Segments | Switzerland
Segment Reporting Information [Line Items]
Revenue	315.0	332.2	631.0	677.1
Adjusted OIBDA	169.7	189.0	332.8	375.5
Operating Segments | Central and Eastern Europe
Segment Reporting Information [Line Items]
Revenue	119.1	123.3	238.2	252.8
Adjusted OIBDA	57.9	62.0	115.1	124.3
Operating Segments | Central and Corporate
Segment Reporting Information [Line Items]
Revenue	60.2	72.9	120.9	125.6
Adjusted OIBDA	(89.5)	(87.9)	(175.2)	(195.0)
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	(1.1)	(1.6)	(2.1)	(3.0)
Adjusted OIBDA	$ 0.0	$ (6.9)	$ 1.4	$ (7.1)