INCOME TAXES - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Non-current Deferred Tax Asset (Liability)
Accumulated net operating losses of TRS	$ 269	$ 337
Unrealized gain	(238)	(251)
Capitalized transaction costs	120	122
Deferred income	71	57
AMT Credit	0	19	$ 12
Deferred tax asset (liability)	698	786
Valuation allowance	(698)	(767)
Net non-current deferred tax asset (liability)	$ 0	$ 19