STOCKHOLDERS' EQUITY (AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Loss
Total after-tax amount	$ 582,491		$ 582,491		$ 588,728
Impact on unrecognized net actuarial loss
Change in the unrecognized net actuarial loss, after tax	(1,931)	$ 2,379	(5,435)	$ 548
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss
Total pre-tax amount	(43,991)		(43,991)		(38,507)
Total after-tax amount	(30,843)	(20,950)	(30,843)	(20,950)	(27,496)	$ (23,479)
Unrecognized Net Periodic Benefit Costs
Accumulated Other Comprehensive Loss
Total pre-tax amount	(40,311)		(40,311)		(35,231)
Total after-tax amount	(28,601)	(19,540)	(28,601)	(19,540)	(25,497)	(22,387)
Interest Rate Swap
Accumulated Other Comprehensive Loss
Total pre-tax amount	(2,035)		(2,035)		(897)
Total after-tax amount	(1,237)	(470)	(1,237)	(470)	(545)	(350)
Foreign Currency Translation
Accumulated Other Comprehensive Loss
Total pre-tax amount	(1,645)		(1,645)		(2,379)
Total after-tax amount	$ (1,005)	$ (940)	$ (1,005)	$ (940)	$ (1,454)	$ (742)