FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Assets and Liabilities) (Details) - Recurring basis - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets:
Assets	$ 24,622	$ 45,613
Cash and cash equivalents
Assets:
Money market funds	21,566	42,470
Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	3,004	2,342
Interest rate swaps	52	801
Accrued expenses
Liabilities:
Contingent consideration		4,472
Other long-term liabilities
Liabilities:
Interest rate swap	548
Level 1
Assets:
Assets	24,570	44,812
Level 1 | Cash and cash equivalents
Assets:
Money market funds	21,566	42,470
Level 1 | Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	3,004	2,342
Level 2
Assets:
Assets	52	801
Level 2 | Other long-term assets
Assets:
Interest rate swaps	52	801
Level 2 | Other long-term liabilities
Liabilities:
Interest rate swap	$ 548
Level 3 | Accrued expenses
Liabilities:
Contingent consideration		$ 4,472