Segment Reporting (Revenue by Major Category) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 4,156.1	$ 3,519.0
Cable [Member]
Segment Reporting Information [Line Items]
Revenue	3,086.3	2,649.9
Cable Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	2,917.1	2,524.7
Cable Video Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	1,198.5	1,054.4
Cable Broadband Internet Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	1,138.8	944.6
Cable Fixed-line Telephony Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	579.8	525.7
Cable Non-Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	169.2	125.2
Residential [Member]
Segment Reporting Information [Line Items]
Revenue	3,521.8	3,030.5
Mobile Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	254.0	244.2
Mobile Non-Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	181.5	136.4
Mobile Residential [Member]
Segment Reporting Information [Line Items]
Revenue	435.5	380.6
Business to Business [Member]
Segment Reporting Information [Line Items]
Revenue	571.4	439.5
Business to Business Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	148.5	105.4
Business to Business Non-Subscription [Member]
Segment Reporting Information [Line Items]
Revenue	422.9	334.1
Other Category [Member]
Segment Reporting Information [Line Items]
Revenue	$ 62.9	$ 49.0