ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent [Roll Forward]
OCI Before Reclassifications			$ 1,900	$ (2,800)
Amounts Reclassified from AOCI			4,900	4,500
Net OCI	$ 1,406	$ (680)	6,821	1,667
Total
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(66,400)	(65,300)
Ending balance	(59,600)	(63,600)	(59,600)	(63,600)
Qualified Cash Flow Hedging Instruments
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(6,200)	(8,200)
OCI Before Reclassifications			0	0
Amounts Reclassified from AOCI			1,600	1,600
Net OCI			1,600	1,600
Ending balance	(4,600)	(6,600)	(4,600)	(6,600)
Unrealized Losses on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance			0	400
OCI Before Reclassifications			(700)	700
Amounts Reclassified from AOCI			0	0
Net OCI			(700)	700
Ending balance	(700)	1,100	(700)	1,100
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(60,200)	(57,500)
OCI Before Reclassifications			2,600	(3,500)
Amounts Reclassified from AOCI			3,300	2,900
Net OCI			5,900	(600)
Ending balance	$ (54,300)	$ (58,100)	$ (54,300)	$ (58,100)