OPERATING SEGMENTS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 segment	Mar. 31, 2013	Dec. 31, 2013
OPERATING SEGMENTS
Number of reportable segments	2
OPERATING SEGMENTS
Revenue	$ 53,354	$ 42,899
Direct operating costs	22,621	21,084
Transportation costs	8,613	6,433
Gross profit	22,120	15,382
Selling, general & administrative expenses	6,636	5,726
Operating income	15,484	9,656
Interest income (expense), net	(42)	(216)
Foreign currency gain (loss)	(940)	(938)
Other income	86	97
Income before income taxes	14,588	8,599
Income tax expense	5,227	3,193
Net income	9,361	5,406
Depreciation, amortization & accretion	4,521	4,113
Capital expenditures	4,775	6,752
Total assets	300,156	219,946	300,556
Treatment and disposal
OPERATING SEGMENTS
Revenue	44,947	36,344
Transportation services
OPERATING SEGMENTS
Revenue	8,407	6,555
Operating Segment | Operating Disposal Facilities
OPERATING SEGMENTS
Revenue	53,349	42,895
Direct operating costs	22,571	21,031
Transportation costs	8,613	6,433
Gross profit	22,165	15,431
Selling, general & administrative expenses	2,599	2,646
Operating income	19,566	12,785
Interest income (expense), net	3	4
Foreign currency gain (loss)	380	112
Other income	84	95
Income before income taxes	20,033	12,996
Net income	20,033	12,996
Depreciation, amortization & accretion	4,459	4,051
Capital expenditures	4,550	6,726
Total assets	155,032	211,620
Operating Segment | Operating Disposal Facilities | Treatment and disposal
OPERATING SEGMENTS
Revenue	44,942	36,340
Operating Segment | Operating Disposal Facilities | Transportation services
OPERATING SEGMENTS
Revenue	8,407	6,555
Operating Segment | Non-Operating Disposal Facilities
OPERATING SEGMENTS
Revenue	5	4
Direct operating costs	50	53
Gross profit	(45)	(49)
Operating income	(45)	(49)
Other income	2	2
Income before income taxes	(43)	(47)
Net income	(43)	(47)
Depreciation, amortization & accretion	48	52
Capital expenditures	43
Total assets	117	86
Operating Segment | Non-Operating Disposal Facilities | Treatment and disposal
OPERATING SEGMENTS
Revenue	5	4
Corporate
OPERATING SEGMENTS
Selling, general & administrative expenses	4,037	3,080
Operating income	(4,037)	(3,080)
Interest income (expense), net	(45)	(220)
Foreign currency gain (loss)	(1,320)	(1,050)
Income before income taxes	(5,402)	(4,350)
Income tax expense	5,227	3,193
Net income	(10,629)	(7,543)
Depreciation, amortization & accretion	14	10
Capital expenditures	182	26
Total assets	$ 145,007	$ 8,240