FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Assets and Liabilities) (Details) - Recurring basis - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Assets:
Assets	$ 24,534	$ 7,923
Liabilities:
Liabilities	7,021	7,317
Cash and cash equivalents
Assets:
Money market funds	22,217	5,703
Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	2,231	2,220
Interest rate swap	86
Accrued and other long term liabilities
Liabilities:
Contingent consideration	6,790	6,775
Other long-term liabilities
Liabilities:
Interest rate swap	231	542
Level 1
Assets:
Assets	24,448	7,923
Level 1 | Cash and cash equivalents
Assets:
Money market funds	22,217	5,703
Level 1 | Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	2,231	2,220
Level 2
Assets:
Assets	86
Liabilities:
Liabilities	231	542
Level 2 | Other long-term assets
Assets:
Interest rate swap	86
Level 2 | Other long-term liabilities
Liabilities:
Interest rate swap	231	542
Level 3
Liabilities:
Liabilities	$ 6,790	$ 6,775
Level 3 | LDS
Liabilities:
Discount rate (as a percent)	12.30%	12.30%
Level 3 | Accrued and other long term liabilities
Liabilities:
Contingent consideration	$ 6,790	$ 6,775