BENEFIT PLANS (Combined Funded Status of Plans and their Reconciliation with Related Amounts Recognized in Consolidated Financial Statements II) (Details) - Postretirement Benefits [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in Benefit Obligation
Projected benefit obligation at beginning of year	$ 45,546	$ 48,605
Service cost	1,167	1,123	$ 1,894
Interest cost	1,260	1,209	2,485
Actuarial loss (gain)	378	(111)
Benefits paid	(4,871)	(5,280)	(5,915)
Projected benefit obligation at end of year	43,480	45,546	48,605
Change in Fair Value of Plan Assets
Fair value of assets at beginning of year	0	0
Actual return on plan assets	0	0
Fair value of assets at end of year	0	0	$ 0
Funded status	(43,480)	(45,546)
Amounts Recognized in the Consolidated Balance Sheets
Current liabilities	(5,624)	(6,013)
Noncurrent liabilities	(37,856)	(39,533)
Net amount recognized	(43,480)	(45,546)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial gain	(20,757)	(22,685)
Prior service credit	(15,456)	(19,692)
Total amount recognized	$ (36,213)	$ (42,377)