Segment Reporting (Balance Sheet Data of Reportable Segments) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total assets	$ 53,153.6	$ 57,596.8
VodafoneZiggo JV
Segment Reporting Information [Line Items]
Long-lived assets	22,026.2	24,017.4
Total assets	23,255.3	24,900.2
Total - continuing operations
Segment Reporting Information [Line Items]
Long-lived assets	28,629.0	30,114.7
Total assets	42,622.5	46,083.4
U.K./Ireland | Total - continuing operations
Segment Reporting Information [Line Items]
Long-lived assets	16,254.6	17,678.3
Total assets	20,702.5	21,968.4
Belgium | Total - continuing operations
Segment Reporting Information [Line Items]
Long-lived assets	5,979.4	6,067.9
Total assets	6,972.1	6,992.8
Switzerland | Total - continuing operations
Segment Reporting Information [Line Items]
Long-lived assets	4,165.4	4,212.5
Total assets	4,496.0	4,528.9
Central and Eastern Europe | Total - continuing operations
Segment Reporting Information [Line Items]
Long-lived assets	1,087.4	1,161.2
Total assets	1,130.8	1,191.8
Central and Corporate | Total - continuing operations
Segment Reporting Information [Line Items]
Long-lived assets	1,142.2	994.8
Total assets	$ 9,321.1	$ 11,401.5