Debt (Refinancing Transactions) (Details)
 1 Months Ended 4 Months Ended 12 Months Ended
Oct. 31, 2019
USD ($)
Oct. 31, 2019
EUR (€)
Oct. 31, 2019
GBP (£)
Aug. 31, 2019
USD ($)
Jul. 31, 2019
USD ($)
Jul. 31, 2019
EUR (€)
May 31, 2019
USD ($)
May 31, 2019
GBP (£)
Aug. 31, 2019
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Oct. 31, 2019
EUR (€)
Oct. 31, 2019
GBP (£)
Aug. 31, 2019
GBP (£)
May 31, 2019
GBP (£)
Debt Instrument [Line Items]                                
Non-cash borrowings and repayments of debt                   $ 3,300,200,000 $ 2,583,300,000 $ 17,104,000,000.0        
Losses on debt modification and extinguishment $ 50,700,000                              
VM Dollar Senior Secured Notes                                
Debt Instrument [Line Items]                                
Extinguishment of debt 1,000,000,000.0                              
VM Sterling Senior Secured Notes                                
Debt Instrument [Line Items]                                
Extinguishment of debt 397,900,000   £ 300,000,000.0                          
VM Credit Facility                                
Debt Instrument [Line Items]                                
Extinguishment of debt 3,400,000,000.0                              
Telenet Credit Facility                                
Debt Instrument [Line Items]                                
Extinguishment of debt 416,600,000 € 371,000,000.0                            
Senior Notes                                
Debt Instrument [Line Items]                                
Losses on debt modification and extinguishment                 $ 77,200,000              
Payment for debt redemption premium                 75,800,000              
Write-off of unamortized debt discount and deferred financing cost                 1,400,000              
Senior Notes | Virgin Media                                
Debt Instrument [Line Items]                                
Losses on debt modification and extinguishment 67,400,000                   36,400,000          
Payment for debt redemption premium 46,000,000.0                   28,200,000          
Write-off of unamortized debt discount and deferred financing cost 21,400,000                   8,200,000 40,600,000        
Senior Notes | Telenet                                
Debt Instrument [Line Items]                                
Extinguishment of debt       $ 1,645,000,000.0 $ 119,000,000.0 € 106,000,000.0                    
Losses on debt modification and extinguishment       15,400,000 4,000,000.0                      
Payment for debt redemption premium 46,800,000       3,600,000                      
Write-off of unamortized debt discount and deferred financing cost 3,900,000       400,000                      
Senior Notes | VM Dollar Senior Secured Notes                                
Debt Instrument [Line Items]                                
Extinguishment of debt             $ 802,400,000                  
Senior Notes | VM Sterling Senior Secured Notes                                
Debt Instrument [Line Items]                                
Extinguishment of debt             708,400,000 £ 534,100,000                
Senior Notes | VM Sterling Senior Notes                                
Debt Instrument [Line Items]                                
Extinguishment of debt | £               £ 300,000,000.0                
Senior Notes | UPC Holding Senior Notes                                
Debt Instrument [Line Items]                                
Losses on debt modification and extinguishment                       112,100,000        
Payment for debt redemption premium                       84,300,000        
Write-off of unamortized debt discount and deferred financing cost                       27,800,000        
Long-term Debt | Virgin Media                                
Debt Instrument [Line Items]                                
Losses on debt modification and extinguishment                       67,500,000        
Payment for debt redemption premium                       32,600,000        
Write-off of unamortized debt discount and deferred financing cost                       7,000,000.0        
Third-party debt modification costs                       1,300,000        
Line of Credit | UPC Holding                                
Debt Instrument [Line Items]                                
Losses on debt modification and extinguishment                     8,900,000          
Payment for debt redemption premium                     2,000,000.0          
Write-off of unamortized debt discount and deferred financing cost                     6,900,000          
Senior Notes | VM Dollar Senior Secured Notes                                
Debt Instrument [Line Items]                                
Original issue amount         $ 600,000,000.0   825,000,000.0                  
Senior Notes | VM Sterling Senior Secured Notes                                
Debt Instrument [Line Items]                                
Original issue amount       $ 53,100,000     $ 397,900,000   $ 53,100,000           £ 40,000,000.0 £ 300,000,000.0
Senior Notes | VM Sterling-Denominated Term Loan Facility                                
Debt Instrument [Line Items]                                
Original issue amount 530,500,000                         £ 400,000,000.0    
Medium-term Notes | Telenet                                
Debt Instrument [Line Items]                                
Losses on debt modification and extinguishment                     31,500,000 75,700,000        
Payment for debt redemption premium                     19,300,000 21,500,000        
Write-off of unamortized debt discount and deferred financing cost                     $ 12,200,000 $ 54,200,000        
Medium-term Notes | VM Dollar-Denominated Term Loan Facility                                
Debt Instrument [Line Items]                                
Original issue amount 3,300,000,000.0                              
Medium-term Notes | VM Euro-Denominated Term Loan Facility                                
Debt Instrument [Line Items]                                
Original issue amount 842,100,000                       € 750,000,000.0      
Medium-term Notes | Telenet Dollar-Denominated Term Loan Facility                                
Debt Instrument [Line Items]                                
Original issue amount 220,000,000.0                              
Medium-term Notes | Telenet Euro-Denominated Term Loan Facility                                
Debt Instrument [Line Items]                                
Original issue amount $ 196,500,000                       € 175,000,000.0