Fair Value Measurements (Assets and Liabilities Reconciliation) (Schedule and Footnote) (Details) $ in Millions	9 Months Ended
Sep. 30, 2021 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of net assets at January 1, 2021	$ 800.5
Gains included in earnings from continuing operations
Realized and unrealized gains on derivative instruments, net	74.3
Realized and unrealized gains due to changes in fair values of certain investments and debt, net	646.3
Additions	83.9
Derivative instruments contributed to the VMED O2 JV in connection with the U.K. JV Transaction	(179.3)
Foreign currency translation adjustments and other, net	(21.7)
Balance of net assets at September 30, 2021	1,163.2
Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of net assets at January 1, 2021	519.6
Gains included in earnings from continuing operations
Realized and unrealized gains on derivative instruments, net	0.0
Realized and unrealized gains due to changes in fair values of certain investments and debt, net	467.0
Additions	83.9
Derivative instruments contributed to the VMED O2 JV in connection with the U.K. JV Transaction	0.0
Foreign currency translation adjustments and other, net	(21.7)
Balance of net assets at September 30, 2021	1,048.8
Cross-currency, interest rate and foreign currency derivative contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of net assets at January 1, 2021	0.0
Gains included in earnings from continuing operations
Realized and unrealized gains on derivative instruments, net	0.0
Realized and unrealized gains due to changes in fair values of certain investments and debt, net	179.3
Additions	0.0
Derivative instruments contributed to the VMED O2 JV in connection with the U.K. JV Transaction	(179.3)
Foreign currency translation adjustments and other, net	0.0
Balance of net assets at September 30, 2021	0.0
Equity-related derivative instruments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of net assets at January 1, 2021	280.9
Gains included in earnings from continuing operations
Realized and unrealized gains on derivative instruments, net	74.3
Realized and unrealized gains due to changes in fair values of certain investments and debt, net	0.0
Additions	0.0
Derivative instruments contributed to the VMED O2 JV in connection with the U.K. JV Transaction	0.0
Foreign currency translation adjustments and other, net	0.0
Balance of net assets at September 30, 2021	114.4
ITV Collar
Gains included in earnings from continuing operations
Settlement of ITV Collar	(240.8)
ITV Collar \| Investments
Gains included in earnings from continuing operations
Settlement of ITV Collar	0.0
ITV Collar \| Cross-currency, interest rate and foreign currency derivative contracts
Gains included in earnings from continuing operations
Settlement of ITV Collar	0.0
ITV Collar \| Equity-related derivative instruments
Gains included in earnings from continuing operations
Settlement of ITV Collar	$ (240.8)

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Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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