SEGMENT REPORTING - Reconciliation of Adjusted EBITDA to Loss from Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Adjusted EBITDA
Segment Adjusted EBITDA	$ 14,481	$ 13,312	$ 43,033	$ 43,786
Add (deduct):
Amortization of deferred financing costs	216	216	646	646
Deferred income taxes	(731)	(647)	(3,269)	(293)
Changes in accounts receivable and other assets	5,836	2,822	(578)	1,512
Changes in accounts payable and accrued expenses	(4,767)	2,033	(1,789)	947
Changes in deferred revenue and other liabilities	(150)	(1,176)	(386)	(3,913)
Interest expense, net	(2,827)	(2,384)	(8,025)	(7,500)
Benefit from income taxes	430	605	2,247	1,806
Foreign currency transaction gain (loss)	89	457	183	527
Other income	0	4	0	25
Non-cash contract asset	51	0	154	0
Net cash provided by operating activities	12,628	15,242	32,216	37,543
Operating Segments | Terminalling services
Segment Adjusted EBITDA
Segment Adjusted EBITDA	15,814	14,076	47,197	46,336
Add (deduct):
Benefit from income taxes	431	770	2,265	2,140
Foreign currency transaction gain (loss)	30	20	(32)	33
Operating Segments | Fleet services
Segment Adjusted EBITDA
Segment Adjusted EBITDA	(162)	383	(1)	1,202
Add (deduct):
Benefit from income taxes	(5)	(196)	(21)	(511)
Foreign currency transaction gain (loss)	(3)	(4)	4	(6)
Corporate
Segment Adjusted EBITDA
Segment Adjusted EBITDA	(1,171)	(1,147)	(4,163)	(3,752)
Add (deduct):
Benefit from income taxes	4	31	3	177
Foreign currency transaction gain (loss)	$ 62	$ 441	$ 211	$ 500