Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Management fee, percentage	8.00%
Service fee retained by Sprint	8.60%
Management fee on prepaid wireless revenues and costs	6.00%
Wireless contract asset balance	$ 70.4	$ 65.7	$ 51.1
Payments increasing wireless contract asset balance	18.2
Amortization to reduce revenue	$ 13.5
Cable
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Installation revenue, recognition period	10 months
Commissions and other costs, recognition period (in months)	44 months
Wireline
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Installation revenue, recognition period	11 months
Commissions and other costs, recognition period (in months)	72 months
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reimbursement payment, cost of equipment and commissions, benefit period for recognition	21 months
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reimbursement payment, cost of equipment and commissions, benefit period for recognition	53 months