Long-lived Assets (Schedule of PP&E) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 27,594.8	$ 26,970.3
Accumulated depreciation	(13,783.4)	(13,091.4)
Total property and equipment, net	13,811.4	13,878.9
Distribution systems
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	18,140.6	17,845.4
Customer premises equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,357.5	4,191.2
Support equipment, buildings and land
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 5,096.7	$ 4,933.7