BENEFIT PLANS (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plans, Defined Benefit [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 1,336	$ 1,213
Interest cost	9,126	11,037
Expected return on plan assets	(12,891)	(13,684)
Amortization of prior service cost (credit)	(11)	12
Amortization of actuarial loss (gain)	1,541	5,454
Net periodic pension/postretirement benefit cost (credit)	(899)	4,032
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Pretax reclassification from AOCI included in net periodic pension/postretirement benefit cost (credit)	1,530	5,466
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of Net Periodic Benefit Cost
Service cost	281	473
Interest cost	302	617
Amortization of prior service cost (credit)	(1,059)	(1,058)
Amortization of actuarial loss (gain)	(438)	(4)
Net periodic pension/postretirement benefit cost (credit)	(914)	28
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Pretax reclassification from AOCI included in net periodic pension/postretirement benefit cost (credit)	$ (1,497)	$ (1,062)