Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule of Investments [Line Items]
Revenue	$ 1,854.5	$ 1,746.3	$ 5,570.9	$ 5,353.8
Other assets, current	747.5		747.5		$ 736.3
Dividend distributions received from the VMO2 JV			815.2	266.9
Proceeds from sale of debt securities	1,800.0	2,600.0	6,000.0	7,500.0
Realized net losses	20.1	1.5	52.8	7.6
UK JV Services
Schedule of Investments [Line Items]
Revenue	34.2	59.8	155.4	192.4
VMO2 JV
Schedule of Investments [Line Items]
Revenue	3,503.8	3,042.1	10,058.0	9,642.7
Dividend distributions received from the VMO2 JV				201.0
Dividends received				467.9
Return of capital for cash flow statement				266.9
VMO2 JV | Related Party
Schedule of Investments [Line Items]
Other assets, current	33.3		33.3		37.0
JV Services
Schedule of Investments [Line Items]
Revenue	37.3	75.4	157.8	192.7
VodafoneZiggo JV
Schedule of Investments [Line Items]
Revenue	1,125.2	$ 1,041.7	3,297.0	3,237.3
Dividends received			0.0	186.9
VodafoneZiggo JV | Related Party
Schedule of Investments [Line Items]
Other assets, current	$ 37.9		37.9		$ 35.0
VMO2 JV
Schedule of Investments [Line Items]
Dividends received			$ 0.0	$ 201.0