FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Assets and Liabilities) (Details) - Recurring basis - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Assets	$ 41,108	$ 22,967
Cash and cash equivalents
Assets:
Money market funds	38,003	20,540
Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	3,105	2,427
Other long-term liabilities
Liabilities:
Interest rate swap	2,148	563
Level 1
Assets:
Assets	41,108	22,967
Level 1 | Cash and cash equivalents
Assets:
Money market funds	38,003	20,540
Level 1 | Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	3,105	2,427
Level 2 | Other long-term liabilities
Liabilities:
Interest rate swap	$ 2,148	$ 563