Share-based Compensation (Summary Of Stock-Based Compensation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 206.0	$ 162.2	$ 268.1
Other operating expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	4.4	4.7	3.4
SG&A expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	201.6	157.5	264.7
Liberty Global Plc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	184.3	131.4	247.0
Performance-based incentive awards | Liberty Global Plc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	50.8	23.9	150.6
Non-performance based share-based incentive awards | Liberty Global Plc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	90.1	93.8	96.4
Other | Liberty Global Plc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	43.4	13.7	0.0
Telenet share-based incentive awards | Telenet
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	19.6	20.7	12.2
Other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 2.1	$ 10.1	$ 8.9