INCOME TAXES - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Non-current Deferred Tax Asset (Liability)
Accumulated net operating losses of TRS	$ 99	$ 337
Unrealized gain	191	251
Capitalized transaction costs	114	122
Deferred income	103	57
AMT Credit	19	19	$ 19
Deferred tax asset (liability)	526	786
Valuation allowance	(507)	(767)
Net non-current deferred tax asset (liability)	$ 19	$ 19