Segment Reporting (Revenue and Long-Lived Assets by Geographic Segments) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Segment Reporting Information [Line Items]                      
Revenue                 $ 11,541.5 $ 11,957.9 $ 11,276.4
Long-lived assets $ 28,470.7       $ 28,629.0       28,470.7 28,629.0  
Revenue 2,982.2 $ 2,840.9 $ 2,850.4 $ 2,868.0 2,949.1 $ 2,929.7 $ 3,015.6 $ 3,063.5 11,541.5 11,957.9 11,276.4
VodafoneZiggo JV                      
Segment Reporting Information [Line Items]                      
Long-lived assets 20,674.8       22,026.2       20,674.8 22,026.2  
Revenue                 4,407.8 4,602.2 4,512.5
U.K.                      
Segment Reporting Information [Line Items]                      
Long-lived assets 15,422.4       15,489.2       15,422.4 15,489.2  
Belgium                      
Segment Reporting Information [Line Items]                      
Long-lived assets 5,910.3       5,979.4       5,910.3 5,979.4  
Switzerland                      
Segment Reporting Information [Line Items]                      
Long-lived assets 4,247.7       4,165.4       4,247.7 4,165.4  
Ireland                      
Segment Reporting Information [Line Items]                      
Long-lived assets 748.5       765.4       748.5 765.4  
Poland                      
Segment Reporting Information [Line Items]                      
Long-lived assets 937.0       958.7       937.0 958.7  
Slovakia                      
Segment Reporting Information [Line Items]                      
Long-lived assets 125.2       128.7       125.2 128.7  
U.S. and other                      
Segment Reporting Information [Line Items]                      
Long-lived assets 1,079.6       1,142.2       1,079.6 1,142.2  
Operating Segments | U.K.                      
Segment Reporting Information [Line Items]                      
Revenue                 6,086.2 6,351.2 5,927.9
Operating Segments | Belgium                      
Segment Reporting Information [Line Items]                      
Revenue                 2,893.0 2,993.6 2,865.3
Operating Segments | Switzerland                      
Segment Reporting Information [Line Items]                      
Revenue                 1,258.8 1,326.0 1,370.1
Operating Segments | Ireland                      
Segment Reporting Information [Line Items]                      
Revenue                 514.1 523.9 470.8
Operating Segments | Poland                      
Segment Reporting Information [Line Items]                      
Revenue                 425.7 440.7 417.9
Operating Segments | Slovakia                      
Segment Reporting Information [Line Items]                      
Revenue                 49.7 51.5 49.6
Geography Eliminations                      
Segment Reporting Information [Line Items]                      
Revenue                 314.0 271.0 $ 174.8
Total - continuing operations                      
Segment Reporting Information [Line Items]                      
Long-lived assets $ 28,470.7       $ 28,629.0       $ 28,470.7 $ 28,629.0