REVENUE RECOGNITION, Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Contract with Customer, Asset and Liability [Abstract]
Accounts Receivable	$ 6,071	$ 6,034
Total Deferred Revenue	1,252	1,256
Refund Liability	3,300
Tariff Revenue [Member]
Contract with Customer, Asset and Liability [Abstract]
Accounts Receivable	5,751	5,631
Contract Assets	2,367	2,397
Total Deferred Revenue	1,025	1,053
Refund Liability	3,298	0
Deferred Revenue	1,100
Non-Tariff Revenue [Member]
Contract with Customer, Asset and Liability [Abstract]
Accounts Receivable	320	403
Total Deferred Revenue	227	$ 203
Deferred Revenue	$ 183

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount of liability for consideration received or receivable from customer which is not included in transaction price, when consideration is expected to be refunded to customer.

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