Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Capitalized interest expense	$ 1.0	$ 0.7	$ 0.7
Interest	131.7	65.7	71.1
Income taxes, net of refunds	(13.8)	(12.9)	1.7
Stock consideration for acquisition of Hawaiian Telcom	121.2	0.0	0.0
Accrual of CyrusOne dividends	0.0	0.0	1.1
Acquisition of property by assuming debt and other financing arrangements	51.5	17.3	12.0
Acquisition of property on account	$ 35.8	$ 12.0	$ 23.8