Segment Reporting (Revenue by Major Category) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 1,901.4	$ 2,845.4	$ 8,390.5	$ 8,233.7
Total residential fixed revenue
Segment Reporting Information [Line Items]
Revenue	805.9	1,787.9	4,406.4	5,254.3
Total subscription revenue
Segment Reporting Information [Line Items]
Revenue	780.4	1,740.1	4,278.5	5,119.6
Broadband internet
Segment Reporting Information [Line Items]
Revenue	366.4	799.7	2,008.5	2,333.7
Video
Segment Reporting Information [Line Items]
Revenue	302.6	612.2	1,537.5	1,799.2
Fixed-line telephony
Segment Reporting Information [Line Items]
Revenue	111.4	328.2	732.5	986.7
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	25.5	47.8	127.9	134.7
Total residential revenue
Segment Reporting Information [Line Items]
Revenue	1,331.9	2,217.9	6,304.9	6,421.7
Total residential mobile revenue
Segment Reporting Information [Line Items]
Revenue	526.0	430.0	1,898.5	1,167.4
Subscription revenue
Segment Reporting Information [Line Items]
Revenue	376.0	250.7	1,271.3	713.4
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	150.0	179.3	627.2	454.0
Total B2B revenue
Segment Reporting Information [Line Items]
Revenue	346.5	490.0	1,493.4	1,399.5
Subscription revenue
Segment Reporting Information [Line Items]
Revenue	139.1	149.0	482.1	403.5
Non-subscription revenue
Segment Reporting Information [Line Items]
Revenue	207.4	341.0	1,011.3	996.0
Other revenue
Segment Reporting Information [Line Items]
Revenue	$ 223.0	$ 137.5	$ 592.2	$ 412.5