ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Accumulated Other Comprehensive Income (loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent [Roll Forward]
Beginning balance			$ 10,711,734
OCI Before Reclassifications				$ (1,300)
Amounts Reclassified from AOCL				2,700
Net OCI	$ (794)	$ (189)	2,347	1,480
Ending balance	10,885,523		10,885,523
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(65,300)	(66,800)
OCI Before Reclassifications			(900)
Amounts Reclassified from AOCL			3,300
Net OCI			2,400
Ending balance	(62,900)	(65,400)	(62,900)	(65,400)
Qualified Cash Flow Hedging Instruments [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(8,200)	(10,300)
OCI Before Reclassifications			0	0
Amounts Reclassified from AOCL			1,100	1,100
Net OCI			1,100	1,100
Ending balance	(7,100)	(9,200)	(7,100)	(9,200)
Unrealized Gains/(Losses) on Marketable Securities [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance			400	(1,900)
OCI Before Reclassifications			2,600	1,300
Amounts Reclassified from AOCL			0	0
Net OCI			2,600	1,300
Ending balance	3,000	(600)	3,000	(600)
Defined Benefit Plans [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(57,500)	(54,600)
OCI Before Reclassifications			(3,500)	(2,600)
Amounts Reclassified from AOCL			2,200	1,600
Net OCI			(1,300)	(1,000)
Ending balance	$ (58,800)	$ (55,600)	$ (58,800)	$ (55,600)