INCOME TAXES (Income Tax Expense Included in Income Statements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Tax Expense (Benefit)
Federal	$ 0	$ 0	$ 0
State	0	0	0
Total Current Income Tax Expense	0	0	0
Deferred Income Tax Expense
Federal	98,000	60,000	66,000
Federal Investment Tax Credits	(6,000)	(6,000)	(6,000)
State	9,000	5,000	12,000
Total Deferred Income Tax Expense	101,000	59,000	72,000
Total Federal and State Income Tax Expense	$ 100,763	$ 59,376	$ 71,719