v3.10.0.1
Derivative Instruments (Narrative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
May 22, 2018
Derivative [Line Items]        
Gain (loss) on change in credit risk valuation included in realized and unrealized gains (losses) on derivative instruments, net $ (71.1) $ 168.4 $ 26.5  
Assets - derivative instruments 2,496.7 2,127.7    
Virgin Media        
Derivative [Line Items]        
Notional amount of derivative instruments without exchange of notional amounts at inception and maturity 4,700.0      
Cross Currency Interest Rate Contract        
Derivative [Line Items]        
Assets - derivative instruments 1,742.8 $ 1,548.9    
ITV Collar        
Derivative [Line Items]        
Derivative asset fair value $ 704.0      
Number of common stock shares owned (in shares) 398,515,510      
Shares needed to borrow from custody account to hedge exposure (in shares) 400,000,000      
Sumitomo Collar        
Derivative [Line Items]        
Aggregate market value of borrowed Sumitomo shares       $ 159.3
Lionsgate Loan | Common Stock        
Derivative [Line Items]        
Number of common stock shares owned (in shares) 1,250,000      
Lionsgate Loan | Nonvoting Common Stock        
Derivative [Line Items]        
Number of common stock shares owned (in shares) 1,250,000      
Lionsgate Forward        
Derivative [Line Items]        
Derivative asset fair value $ 42.2      
Counterparty Credit Risk        
Derivative [Line Items]        
Assets - derivative instruments $ 617.3