ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Accumulated Other Comprehensive Income (loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AOCI Attributable to Parent [Roll Forward]
Beginning balance	$ 11,086,242
OCI Before Reclassifications		$ 1,700
Amounts Reclassified from AOCI		1,500
Net OCI	3,273	3,141
Ending balance	11,183,714
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(66,400)	(65,300)
OCI Before Reclassifications	(400)
Amounts Reclassified from AOCI	3,700
Net OCI	3,300
Ending balance	(63,100)	(62,100)
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	700	500
Net OCI	700	500
Ending balance	(5,500)	(7,700)
Unrealized Losses on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance	0	400
OCI Before Reclassifications	(400)	1,700
Amounts Reclassified from AOCI	0	0
Net OCI	(400)	1,700
Ending balance	(400)	2,100
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(60,200)	(57,500)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCI	3,000	1,000
Net OCI	3,000	1,000
Ending balance	$ (57,200)	$ (56,500)