STOCKHOLDERS' EQUITY (AOCI comp) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Changes in accumulated other comprehensive loss, net of tax, by component
Balances			$ 599,055
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	$ 781	$ (1,116)	1,391	$ (3,347)
Balances	602,080		602,080
Accumulated Other Comprehensive Loss
Changes in accumulated other comprehensive loss, net of tax, by component
Balances			(23,417)	(27,496)
Other comprehensive income (loss) before reclassifications			(1,442)	(5,678)
Amounts reclassified from accumulated other comprehensive loss			2,833	2,331
OTHER COMPREHENSIVE INCOME (LOSS), net of tax			1,391	(3,347)
Balances	(22,026)	(30,843)	(22,026)	(30,843)
Unrecognized Net Periodic Benefit Costs
Changes in accumulated other comprehensive loss, net of tax, by component
Balances			(21,886)	(25,497)
Other comprehensive income (loss) before reclassifications			(1,569)	(5,435)
Amounts reclassified from accumulated other comprehensive loss			2,833	2,331
OTHER COMPREHENSIVE INCOME (LOSS), net of tax			1,264	(3,104)
Balances	(20,622)	(28,601)	(20,622)	(28,601)
Interest Rate Swap
Changes in accumulated other comprehensive loss, net of tax, by component
Balances			(329)	(545)
Other comprehensive income (loss) before reclassifications			216	(692)
OTHER COMPREHENSIVE INCOME (LOSS), net of tax			216	(692)
Balances	(113)	(1,237)	(113)	(1,237)
Foreign Currency Translation
Changes in accumulated other comprehensive loss, net of tax, by component
Balances			(1,202)	(1,454)
Other comprehensive income (loss) before reclassifications			(89)	449
OTHER COMPREHENSIVE INCOME (LOSS), net of tax			(89)	449
Balances	$ (1,291)	$ (1,005)	$ (1,291)	$ (1,005)