GOVERNMENT GRANTS (Details) - Mobility Funds $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
MOBILITY FUND GRANTS
Mobility Funds received	$ 21.1
Period over which a portion of the Mobility Funds is used to offset the costs of supporting the networks	5 years
U.S. Telecom
MOBILITY FUND GRANTS
Grant funds used to offset operating expenses	$ 13.9
Mobility funds received and recorded to date	10.5
U.S. Telecom | Property, Plant and Equipment
MOBILITY FUND GRANTS
Grant funds used to offset fixed asset related costs	7.2
U.S. Telecom | Other long-term liabilities
MOBILITY FUND GRANTS
Mobility Funds received	$ 3.4