INTANGIBLE ASSETS OTHER THAN GOODWILL (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Intangible assets other than goodwill
Cost	$ 56,319	$ 48,848
Accumulated Amortization	24,872	17,690
Net	31,447	31,158
Estimated future amortization expense related to intangible assets through 2019
2016	8,688
2017	7,267
2018	4,416
2019	2,610
2020	2,081
Trade names
Intangible assets other than goodwill
Cost	46	46
Accumulated Amortization	23	20
Net	23	26
Patents
Intangible assets other than goodwill
Cost	7,000
Accumulated Amortization	234
Net	6,766
Customer relationships
Intangible assets other than goodwill
Cost	43,922	43,922
Accumulated Amortization	21,267	15,293
Net	22,655	28,629
Supply and transportation agreements
Intangible assets other than goodwill
Cost	3,801	3,330
Accumulated Amortization	2,367	1,769
Net	1,434	1,561
Non-compete agreement
Intangible assets other than goodwill
Cost	1,550	1,550
Accumulated Amortization	981	608
Net	$ 569	$ 942