Segment Reporting (Capital Expenditures of Reportable Segments) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total property and equipment additions	$ 1,683.8	$ 1,839.8
Assets acquired under capital-related vendor financing arrangements	(599.6)	(1,011.7)
Assets acquired under finance leases	(27.8)	(30.9)
Changes in current liabilities related to capital expenditures	58.0	122.7
Total capital expenditures, net	1,114.4	919.9
VMED O2 JV
Segment Reporting Information [Line Items]
Property and equipment additions:	898.8	0.0
VodafoneZiggo JV
Segment Reporting Information [Line Items]
Property and equipment additions:	705.0	685.3
Operating Segments | U.K.
Segment Reporting Information [Line Items]
Total property and equipment additions	557.4	975.3
Operating Segments | Belgium
Segment Reporting Information [Line Items]
Total property and equipment additions	424.5	375.1
Operating Segments | Switzerland
Segment Reporting Information [Line Items]
Total property and equipment additions	413.1	181.8
Operating Segments | Ireland
Segment Reporting Information [Line Items]
Total property and equipment additions	61.9	54.4
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total property and equipment additions	$ 226.9	$ 253.2