v3.8.0.1
SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Summary of the categories of property and equipment    
Property, Plant and Equipment, net of accumulated depreciation $ 347,045 $ 346,507
Deferred Revenue    
Current - accrued compensation and other current liabilities 15,895 17,519
Long-term - other long term liabilities $ 14,250 $ 13,000