Commitments and Contingencies (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 27, 2018	Dec. 31, 2019	Jun. 30, 2019
Telecommunications Capacity
Commitments and Contingencies
Open commitments			$ 75.5
Telecommunications Capacity | Forecast
Commitments and Contingencies
Open commitments met		$ 7.3
Construction Contracts
Commitments and Contingencies
Open commitments			166.4
Pending Litigation
Commitments and Contingencies
Sought amount	$ 21.0
Pending Litigation | Minimum
Commitments and Contingencies
Estimated liability for settlement			1.1
Pending Litigation | Maximum
Commitments and Contingencies
Estimated liability for settlement			$ 2.8
Pending Litigation | Damages Related To Construction Project
Commitments and Contingencies
Sought amount	$ 2.8