Acquisitions (Proforma Information Schedule and Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Revenue	$ 2,949.1	$ 2,929.7	$ 3,015.6	$ 3,063.5	$ 2,987.8	$ 2,899.3	$ 2,746.8	$ 2,642.5	$ 11,957.9	$ 11,276.4	$ 13,731.1
Net earnings (loss)	$ 25.1	$ 974.1	$ 912.6	$ (1,186.5)	$ (992.0)	$ (791.6)	$ (674.3)	$ (320.2)	$ 725.3	$ (2,778.1)	1,705.3
BASE
Business Acquisition [Line Items]
Revenue											597.1
Net earnings (loss)											(2.1)
Liberty Global Shares | BASE
Business Acquisition [Line Items]
Revenue											13,805.5
Net earnings (loss) from continuing operations attributable to Liberty Global shareholders:											$ 1,621.0
Basic (in dollars per share)											$ 1.82
Diluted (in dollars per share)											$ 1.80