Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative [Line Items]
Derivative assets	$ 3,078.3		$ 1,827.5
Cross-currency and interest rate derivative contracts
Derivative [Line Items]
Gain (loss) in changes in the credit risk valuation adjustments associated with our cross-currency and interest rate derivative contracts	66.3	$ (58.1)
Derivative assets	2,019.4		$ 1,157.2
Counterparty Credit Risk
Derivative [Line Items]
Derivative assets	858.2
Virgin Media
Derivative [Line Items]
Derivative instruments that do not involve the exchange of notional amounts at the inception and maturity	$ 2,900.0
Lionsgate Loan
Derivative [Line Items]
Voting shares (in shares)	833,333
Nonvoting shares (in shares)	833,334