STOCKHOLDERS' EQUITY (AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Loss
Total after-tax amount	$ 591,676		$ 599,055
Impact on unrecognized net actuarial loss
Change in the unrecognized net actuarial loss, after tax	(1,471)	$ (3,504)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss
Total pre-tax amount	(30,839)		(31,840)
Total after-tax amount	(22,807)	(29,727)	(23,417)	$ (27,496)
Unrecognized Net Periodic Benefit Costs
Accumulated Other Comprehensive Loss
Total pre-tax amount	(28,737)		(29,320)
Total after-tax amount	(21,530)	(27,766)	(21,886)	(25,497)
Interest Rate Swap
Accumulated Other Comprehensive Loss
Total pre-tax amount	(319)		(542)
Total after-tax amount	(194)	(1,091)	(329)	(545)
Foreign Currency Translation
Accumulated Other Comprehensive Loss
Total pre-tax amount	(1,783)		(1,978)
Total after-tax amount	$ (1,083)	$ (870)	$ (1,202)	$ (1,454)