REVENUE RECOGNITION, Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Contract with Customer, Asset and Liability [Abstract]
Accounts Receivable-Tariff	$ 4,067	$ 6,071
Total Deferred Revenue	1,291	1,252
Tariff Revenue [Member]
Contract with Customer, Asset and Liability [Abstract]
Accounts Receivable-Tariff	3,792	5,751
Contract Assets	2,689	2,367
Total Deferred Revenue	1,026	1,025
Refund Liability	0	3,298
Deferred Revenue	1,000
Non-Tariff Revenue [Member]
Contract with Customer, Asset and Liability [Abstract]
Accounts Receivable-Tariff	275	320
Total Deferred Revenue	265	$ 227
Deferred Revenue	$ 207