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Plant, Property and Equipment, Net - Assets Held for Sale (Details) - USD ($) $ in Millions		6 Months Ended	9 Months Ended
	Aug. 01, 2017	Dec. 31, 2018	Sep. 30, 2017
Assets Held for Sale
Net proceeds from sale of assets			$ 213.0
Chicago fiber network \| Assets Held for Sale
Assets Held for Sale
Assets			149.2
Liabilities			$ 15.5
Construction costs	$ 7.0
Chicago fiber network \| Verizon \| Forecast
Assets Held for Sale
New agreement revenue from build-out of the network		$ 50.0
Chicago fiber network \| Verizon \| Assets Held for Sale
Assets Held for Sale
Net proceeds from sale of assets	$ 225.0