Long-lived Assets (Schedule of PP&E) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 14,274.3	$ 28,646.2
Accumulated depreciation	(7,987.7)	(14,802.8)
Accumulated depreciation	6,286.6	13,843.4
Distribution systems
Property, Plant and Equipment [Line Items]
Property and equipment gross	8,818.0	19,007.2
Customer premises equipment
Property, Plant and Equipment [Line Items]
Property and equipment gross	1,691.2	4,294.7
Support equipment, buildings and land
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 3,765.1	$ 5,344.3