SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Summary of the categories of property and equipment
Property, Plant and Equipment, net of accumulated depreciation	$ 327,901	$ 317,030
Deferred Revenue
Current - accrued compensation and other current liabilities	21,208	22,692
Long-term - other long term liabilities	$ 700	$ 1,138

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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