FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Assets and Liabilities) (Details) - Recurring basis - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Assets	$ 115,665	$ 22,967
Cash and cash equivalents
Assets:
Money market funds	113,126	20,540
Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	2,539	2,427
Other long-term liabilities
Liabilities:
Interest rate swap	1,912	563
Level 1
Assets:
Assets	115,665	22,967
Level 1 | Cash and cash equivalents
Assets:
Money market funds	113,126	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	2,539	2,427
Level 2 | Other long-term liabilities
Liabilities:
Interest rate swap	$ 1,912	$ 563