RECEIVABLES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
RECEIVABLES
Trade				$ 95,055	$ 116,218
Unbilled revenue				11,983	17,857
Other				2,568	1,890
Total receivables				109,606	135,965
Allowance for doubtful accounts	$ (704)	$ (525)	$ (468)	(3,226)	(704)
Receivables, net				$ 106,380	$ 135,261
Change in the allowance for doubtful accounts receivable
Balance at Beginning of Period	704	525	468
Charged (Credited) to Costs and Expenses	2,224	1,391	138
Deductions/Write-offs	848		(70)
Recoveries (Deductions/ Write-offs)		(1,211)
Adjustments	(550)	(1)	(11)
Balance at End of Period	$ 3,226	$ 704	$ 525