Commitments and Contingencies (Narrative) (Details) € in Millions	1 Months Ended				9 Months Ended
	Oct. 31, 2019 USD ($)	Oct. 31, 2019 EUR (€)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Oct. 31, 2019 EUR (€)	Aug. 01, 2018
Loss Contingencies [Line Items]
Programming costs					$ 957,900,000	$ 1,176,700,000
Percentage of amounts recovered					50.00%
Percentage of net present value, cost savings					50.00%
Percentage of legal and other third party, fees					50.00%
Belgium Regulatory Developments
Loss Contingencies [Line Items]
Percent of reduction in monthly wholesale cable resale access prices								17.00%
Interkabel Acquisition
Loss Contingencies [Line Items]
Damages sought			$ 1,600,000,000	€ 1,400.0
Loss contingency accrual					$ 0
Deutsche Telekom Litigation
Loss Contingencies [Line Items]
Reduction of annual lease fees					83.33%
Disposed of by sale | UPC Austria
Loss Contingencies [Line Items]
Asserted claims	$ 81,600,000	€ 70.5
Amount of claim	$ 122,900,000						€ 106.2