Long-lived Assets (Schedule of PP&E) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 28,646.2
Total property and equipment, gross		$ 26,970.3
Accumulated depreciation	(14,802.8)
Accumulated depreciation		(13,091.4)
Total property and equipment, net	13,843.4
Total property and equipment, net		13,878.9
Distribution systems
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	19,007.2
Total property and equipment, gross		17,845.4
Customer premises equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,294.7
Total property and equipment, gross		4,191.2
Support equipment, buildings and land
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 5,344.3
Total property and equipment, gross		$ 4,933.7
Minimum | Distribution systems
Property, Plant and Equipment [Line Items]
Estimated useful life at December 31, 2019	3 years
Minimum | Customer premises equipment
Property, Plant and Equipment [Line Items]
Estimated useful life at December 31, 2019	2 years
Minimum | Support equipment, buildings and land
Property, Plant and Equipment [Line Items]
Estimated useful life at December 31, 2019	2 years
Maximum | Distribution systems
Property, Plant and Equipment [Line Items]
Estimated useful life at December 31, 2019	30 years
Maximum | Customer premises equipment
Property, Plant and Equipment [Line Items]
Estimated useful life at December 31, 2019	10 years
Maximum | Support equipment, buildings and land
Property, Plant and Equipment [Line Items]
Estimated useful life at December 31, 2019	50 years