Segment Reporting (Revenue by Major Category) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 3,105.5	$ 2,722.9	$ 6,720.8	$ 5,598.7
Total residential cable revenue
Segment Reporting Information [Line Items]
Revenue	1,714.7	1,778.5	3,800.5	3,649.6
Total subscription revenue
Segment Reporting Information [Line Items]
Revenue	1,667.4	1,742.9	3,696.5	3,561.0
Broadband internet
Segment Reporting Information [Line Items]
Revenue	763.9	781.0	1,690.7	1,577.8
Video
Segment Reporting Information [Line Items]
Revenue	631.5	633.6	1,376.6	1,316.7
Fixed-line telephony
Segment Reporting Information [Line Items]
Revenue	272.0	328.3	629.2	666.5
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	47.3	35.6	104.0	88.6
Total residential revenue
Segment Reporting Information [Line Items]
Revenue	2,327.7	2,135.5	5,175.2	4,387.8
Total residential mobile revenue
Segment Reporting Information [Line Items]
Revenue	613.0	357.0	1,374.7	738.2
Subscription revenue
Segment Reporting Information [Line Items]
Revenue	415.8	227.3	897.1	463.2
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	197.2	129.7	477.6	275.0
Total B2B revenue
Segment Reporting Information [Line Items]
Revenue	572.2	461.6	1,176.4	935.7
Subscription revenue
Segment Reporting Information [Line Items]
Revenue	191.6	133.1	359.6	268.8
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	380.6	328.5	816.8	666.9
Other revenue
Segment Reporting Information [Line Items]
Revenue	$ 205.6	$ 125.8	$ 369.2	$ 275.2