v3.10.0.1

Commitments and Contingencies (Narrative) (Details) € in Millions, £ in Millions	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2015 EUR (€)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 USD ($)	Dec. 31, 2018 GBP (£)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 GBP (£)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 GBP (£)	Nov. 26, 2007 association
Interkabel Acquisition [Member]
Loss Contingencies [Line Items]
Damages sought	€ 1,400.0	$ 1,600,000,000
Interkabel Acquisition [Member]
Loss Contingencies [Line Items]
Number of associations of municipalities in Belgium | association																	4
Loss contingency damages in excess value							€ 20.0								$ 23,400,000
Loss contingency accrual														$ 0
Deutsche Telekom Litigation [Member]
Loss Contingencies [Line Items]
Damages sought							€ 76.0	$ 89,000,000
Reduction of annual lease fees					83.33%		66.67%	66.67%
Belgium Regulatory Developments [Member]
Loss Contingencies [Line Items]
Percent of reduction in monthly wholesale cable resale access prices													17.00%	17.00%
Virgin Media VAT Matters [Member]
Loss Contingencies [Line Items]
Loss contingency accrual														$ 0
Virgin Media VAT Matters [Member] | Maximum
Loss Contingencies [Line Items]
Estimate of possible loss													£ 47.0	62,000,000
Virgin Media VAT Matters 2 [Member]
Loss Contingencies [Line Items]
Estimate of possible loss | £																£ 63.7
Loss contingency accrual														$ 0
Continuing operations			£ 67.0	$ 99,100,000
Interest expense | £			£ 3.3
Other Regulatory Issues [Member] | Maximum | Forecast | U.K.
Loss Contingencies [Line Items]
Estimate of possible loss									£ 110.0	$ 145,000,000	£ 18.0	$ 24,000,000
Broadband Communications and DHT Operations [Member]
Loss Contingencies [Line Items]
Programming costs					$ 805,100,000	$ 720,000,000.0

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