FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details 3) (Recurring basis, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Level 1
Assets and liabilities measured at fair value on a recurring basis
Assets	$ 44,069	$ 15,164
Level 1 | Money market funds
Assets and liabilities measured at fair value on a recurring basis
Assets	41,101	12,101
Level 1 | Voluntary Savings Plan - mutual funds held in trust
Assets and liabilities measured at fair value on a recurring basis
Assets	2,968	3,063
Level 2 | Interest rate swap agreement
Assets and liabilities measured at fair value on a recurring basis
Liabilities	$ 576