Debt Other Financing Arrangements (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Other Installment Financing Arrangements [Line Items]
Other Installment Financing Arrangements	$ 44.3	$ 44.6
Other Liabilities, Current	44.5	39.2
Other Liabilities, Noncurrent	68.5	72.8
Data Center Financing Arrangements [Member]
Other Installment Financing Arrangements [Line Items]
Other Installment Financing Arrangements	4.5	4.5
Pole license agreement obligation [Member]
Other Installment Financing Arrangements [Line Items]
Other Installment Financing Arrangements	39.8	40.1
Other Liabilities, Current	1.0	1.0
Other Liabilities, Noncurrent	$ 38.8	$ 39.1