REVENUE FROM CONTRACTS FROM CUSTOMERS Financial Statement Impact of 606 - Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unbilled receivables	$ 72,809	$ 38,951	$ 37,785
Inventories, net	20,186	20,204	20,496
Prepaid expenses	1,424	1,863	2,266
Accrued expenses	20,007	17,911	17,862
Deferred revenue	7,474	7,833	6,090
Deferred tax liability, net	18,222	18,849	19,174
Accumulated deficit	(116,062)	$ (112,935)	(111,939)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unbilled receivables	71,583		37,785
Inventories, net	21,121		20,496
Prepaid expenses	1,498		2,266
Accrued expenses	20,040		17,862
Deferred revenue	6,981		6,090
Deferred tax liability, net	18,351		19,174
Accumulated deficit	$ (115,948)		$ (111,939)