Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Change in valuation allowances	$ 140.8
Change in valuation allowances	113.6	$ 34.9	$ 341.6
Recorded liability for the Mandatory Repatriation Tax	357.2	293.3
Unrecognized tax benefits - favorable impact on effective income tax rate if ultimately recognized, net of valuation allowances	546.5	759.8	189.3
Reductions to our unrecognized tax benefits reasonably possible	285.0
Income tax penalties and interest expense	22.6	58.9	$ 5.5
Accrued interest and penalties on tax related items	115.1
Virgin Media
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Amount on which future tax deductions can be claimed	$ 18,400.0	$ 18,100.0
Maximum percent of capital allowances claimed allowance	18.00%