STOCKHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Loss
Total after-tax amount	$ 579,204	$ 560,883
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss
Total pre-tax amount	(27,793)	(31,932)
Total after-tax amount	(20,950)	(23,479)	$ (16,783)	$ (14,912)
Unrecognized Net Periodic Benefit Costs
Accumulated Other Comprehensive Loss
Total pre-tax amount	(25,480)	(30,140)
Total after-tax amount	(19,540)	(22,387)	(16,321)	(14,386)
Interest Rate Swap
Accumulated Other Comprehensive Loss
Total pre-tax amount	(773)	(576)
Total after-tax amount	(470)	(350)
Foreign Currency Translation
Accumulated Other Comprehensive Loss
Total pre-tax amount	(1,540)	(1,216)
Total after-tax amount	$ (940)	$ (742)	$ (462)	$ (526)