ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent [Roll Forward]
OCI Before Reclassifications	$ 200	$ 700
Amounts Reclassified from AOCI	1,800	1,500
Other Comprehensive Income (Loss), Net of Tax	1,948	2,196
Total
AOCI Attributable to Parent [Roll Forward]
Balance	(65,100)	(60,000)
Other Comprehensive Income (Loss), Net of Tax	1,948	2,196
Balance	(63,100)	(57,800)
Qualified Cash Flow Hedging Instruments
AOCI Attributable to Parent [Roll Forward]
Balance	(3,000)	(4,400)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCI	200	300
Other Comprehensive Income (Loss), Net of Tax	200	300
Balance	(2,800)	(4,100)
Unrealized Gains on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Balance	700	(500)
OCI Before Reclassifications	200	700
Amounts Reclassified from AOCI	0	0
Other Comprehensive Income (Loss), Net of Tax	200	700
Balance	900	200
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Balance	(62,800)	(55,100)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCI	1,600	1,200
Other Comprehensive Income (Loss), Net of Tax	1,600	1,200
Balance	$ (61,200)	$ (53,900)