Segment Reporting (Revenue by Major Category) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 3,615.3	$ 2,875.8
Total residential cable revenue
Segment Reporting Information [Line Items]
Revenue	2,085.8	1,871.1
Total subscription revenue
Segment Reporting Information [Line Items]
Revenue	2,029.1	1,818.1
Broadband internet
Segment Reporting Information [Line Items]
Revenue	926.8	796.8
Video
Segment Reporting Information [Line Items]
Revenue	745.1	683.1
Fixed-line telephony
Segment Reporting Information [Line Items]
Revenue	357.2	338.2
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	56.7	53.0
Total residential revenue
Segment Reporting Information [Line Items]
Revenue	2,847.5	2,252.3
Total residential mobile revenue
Segment Reporting Information [Line Items]
Revenue	761.7	381.2
Subscription revenue
Segment Reporting Information [Line Items]
Revenue	481.3	235.9
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	280.4	145.3
Total B2B revenue
Segment Reporting Information [Line Items]
Revenue	604.2	474.1
Subscription revenue
Segment Reporting Information [Line Items]
Revenue	147.9	124.6
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	456.3	349.5
Other revenue
Segment Reporting Information [Line Items]
Revenue	$ 163.6	$ 149.4