ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Accumulated Other Comprehensive Income (loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of Beginning of Period			$ (66,844)
Net OCI	$ (253)	$ (1,513)	1,227	$ 463
Balance as of End of Period	(65,617)		(65,617)
AOCI Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of Beginning of Period			(66,800)	(74,000)
OCI Before Reclassifications			(3,000)	(4,300)
Amounts Reclassified from AOCI			4,200	4,800
Net OCI			1,200	500
Balance as of End of Period	(65,600)	(73,500)	(65,600)	(73,500)
Qualified Cash Flow Hedging Instruments [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of Beginning of Period			(10,300)	(12,400)
OCI Before Reclassifications			0	0
Amounts Reclassified from AOCI			1,600	1,500
Net OCI			1,600	1,500
Balance as of End of Period	(8,700)	(10,900)	(8,700)	(10,900)
Unrealized Gains/(Losses) on Marketable Securities [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of Beginning of Period			(1,900)	700
OCI Before Reclassifications			2,300	(3,900)
Amounts Reclassified from AOCI			0	0
Net OCI			2,300	(3,900)
Balance as of End of Period	400	(3,200)	400	(3,200)
Defined Benefit Plans [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of Beginning of Period			(54,600)	(62,300)
OCI Before Reclassifications			(5,300)	(400)
Amounts Reclassified from AOCI			2,600	3,300
Net OCI			(2,700)	2,900
Balance as of End of Period	$ (57,300)	$ (59,400)	$ (57,300)	$ (59,400)