OTHER COMPREHENSIVE INCOME (Amounts Reclassified from Accumulated Other Comprehensive Income to Earnings) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (37,774)	$ (34,076)
Other nonoperating income	5,083	4,045
Benefit from income taxes	(4,903)	(3,175)
Total	52,979	44,921
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total	1,157	747
Amortization of Interest Rate Hedge Losses [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	89	528
Benefit from income taxes	(23)	(208)
Total	66	320
Amortization of Pension and Postretirement Plan Actuarial Loss and Prior Service Cost [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other nonoperating income	1,476	703
Benefit from income taxes	(385)	(276)
Total	$ 1,091	$ 427