INCOME TAXES (The Significant Components of Deferred Income Tax Assets and Liabilities) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Gross Deferred Income Tax Assets
Capital Lease Obligations	$ 48,000,000	$ 10,000,000
Operating Loss Carryforwards, Net	23,000,000	56,000,000
Customer Advances and Contributions in Aid of Construction	16,000,000	14,000,000
Alternative Minimum Tax Credit	13,000,000	26,000,000
Other Postretirement Benefits	15,000,000	15,000,000
Investment Tax Credit Carryforward	34,000,000	34,000,000
Income Taxes Recoverable Through Future Rates	87,000,000	88,000,000
Other	60,000,000	50,000,000
Total Gross Deferred Income Tax Assets	296,000,000	293,000,000
Deferred Tax Assets Valuation Allowance	0	0
Gross Deferred Income Tax Liabilities
Plant, Net	(552,000,000)	(518,000,000)
Plant Abandonments	(18,000,000)	(21,000,000)
Capital Lease Assets, Net	(44,000,000)	(5,000,000)
Pensions	(19,000,000)	(16,000,000)
Income Taxes Payable Through Future Rates	(12,000,000)	(10,000,000)
Other	(21,000,000)	(23,000,000)
Total Gross Deferred Income Tax Liabilities	(666,000,000)	(593,000,000)
Deferred Income Taxes, Net	$ (369,705,000)	$ (300,258,000)