NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Reclassification) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income (Deductions)
Interest Income			$ 0	$ 0
Other Income			0	0
Other Expense			0	0
Appreciation in Value of Investments			0	0
Allowance For Equity Funds		$ 8,117	5,322	4,522
Other, Net		(487)	8,995	353
Interest Expense
Long-Term Debt			0	0
Capital Leases			0	0
Other Interest Expense			0	0
Interest Costs Capitalized Adjustment		(3,151)	(2,078)	(1,710)
Interest Expense		67,620	65,290	65,902
Interest Capitalized
Interest Expense
Interest Costs Capitalized Adjustment			0	0
Allowance For Borrowed Funds
Interest Expense
Interest Costs Capitalized Adjustment			(2,078)	(1,710)
As Filed
Other Income (Deductions)
Interest Income			742	111
Other Income			14,128	5,636
Other Expense			(3,344)	(3,019)
Appreciation in Value of Investments			2,791	2,147
Allowance For Equity Funds			0	0
Other, Net			0	0
Interest Expense
Long-Term Debt			62,018	62,015
Capital Leases			2,554	3,356
Other Interest Expense			718	531
Interest Expense			0	0
As Filed | Interest Capitalized
Interest Expense
Interest Costs Capitalized Adjustment			(2,078)	(1,710)
As Filed | Allowance For Borrowed Funds
Interest Expense
Interest Costs Capitalized Adjustment			0	0
Amount Reclassified
Other Income (Deductions)
Interest Income			(742)	(111)
Other Income			(14,128)	(5,636)
Other Expense			3,344	3,019
Appreciation in Value of Investments			(2,791)	(2,147)
Allowance For Equity Funds			5,322	4,522
Other, Net			8,995	353
Interest Expense
Long-Term Debt			(62,018)	(62,015)
Capital Leases			(2,554)	(3,356)
Other Interest Expense			(718)	(531)
Interest Expense			65,290	65,902
Amount Reclassified | Interest Capitalized
Interest Expense
Interest Costs Capitalized Adjustment			2,078	1,710
Amount Reclassified | Allowance For Borrowed Funds
Interest Expense
Interest Costs Capitalized Adjustment			$ (2,078)	$ (1,710)
Retained Earnings
Interest Expense
Adoption of ASU, Cumulative Effect Adjustment	$ 1,000	878
AOCI Attributable to Parent
Interest Expense
Adoption of ASU, Cumulative Effect Adjustment	$ (1,000)	$ (878)