Restructuring Costs - Summary of Company's Net Pretax Restructuring Charges (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring costs, net	$ 44.4	$ 23.7
Broadband [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs, net	10.4	5.4
Home [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs, net	5.9	3.6
OWN [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs, net	5.8	3.4
VCN [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs, net	$ 22.3	$ 11.3