Asset Sales (Details) - USD ($) $ in Millions		6 Months Ended
Aug. 01, 2017	Jun. 30, 2019
Chicago Fiber Network \| Disposal Group, Held-for-sale, Not Discontinued Operations
Asset Sales
Total assets		$ 15.0
Network elements under the Construction Services Agreement \| Disposal Group Disposed of by Sale, Not Discontinued Operations
Asset Sales
Gain on sale of assets		$ 3.2
Verizon \| Chicago Fiber Network \| Disposal Group Disposed of by Sale, Not Discontinued Operations
Asset Sales
Net proceeds from sale of assets	$ 225.0
Agreement amount for build-out of network	$ 50.0

Amount classified as assets attributable to disposal group held for sale or disposed of.

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