ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($)		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		$ 528,468,000
Other comprehensive gain (loss) before reclassification		15,000	$ (151,000)
Actuarial gain (loss)			(834,000)
Reclassification to net income	[1]	299,000	282,000
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)		314,000	(703,000)
BALANCE		565,151,000
Unrealized gain (loss) on available-for-sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		(246,000)	(111,000)
Other comprehensive gain (loss) before reclassification		(15,000)	(151,000)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)		(15,000)	(151,000)
BALANCE		(261,000)	(262,000)
Net unrealized gain (loss) on retirement plan [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE	[2]	(10,355,000)	(9,708,000)
Actuarial gain (loss)	[2]		(834,000)
Reclassification to net income	[1],[2]	299,000	282,000
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	[2]	299,000	(552,000)
BALANCE	[2]	(10,056,000)	(10,260,000)
Change in cumulative foreign currency translation adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		(65,000)
Other comprehensive gain (loss) before reclassification		30,000
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)		30,000
BALANCE		(35,000)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
BALANCE		(10,666,000)	(9,819,000)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)		314,000
BALANCE		$ (10,352,000)	$ (10,522,000)

[1] The Company reclassified amortization of prior service cost and actuarial loss for its retirement plan from accumulated other comprehensive loss to net income (loss) of $299,000 and $282,000 for the three months ended March 31, 2017 and 2016, respectively.

[2] Refer to Note 13: Supplemental Executive Retirement Plan.