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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent [Roll Forward]
Beginning balance			$ 10,711,734
OCI Before Reclassifications				$ (3,000)
Amounts Reclassified from AOCL				4,200
Net OCI	$ (680)	$ (253)	1,667	1,227
Ending balance	10,998,037		10,998,037
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(65,300)	(66,800)
OCI Before Reclassifications			(2,800)
Amounts Reclassified from AOCL			4,500
Net OCI			1,700
Ending balance	(63,600)	(65,600)	(63,600)	(65,600)
Qualified Cash Flow Hedging Instruments
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(8,200)	(10,300)
OCI Before Reclassifications			0	0
Amounts Reclassified from AOCL			1,600	1,600
Net OCI			1,600	1,600
Ending balance	(6,600)	(8,700)	(6,600)	(8,700)
Unrealized Gains/(Losses) on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance			400	(1,900)
OCI Before Reclassifications			700	2,300
Amounts Reclassified from AOCL			0	0
Net OCI			700	2,300
Ending balance	1,100	400	1,100	400
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(57,500)	(54,600)
OCI Before Reclassifications			(3,500)	(5,300)
Amounts Reclassified from AOCL			2,900	2,600
Net OCI			(600)	(2,700)
Ending balance	$ (58,100)	$ (57,300)	$ (58,100)	$ (57,300)