INCOME TAXES (Income Tax Expense Included in Income Statements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Tax Expense (Benefit)
Federal	$ 0	$ 0	$ (1,000)
State	0	0	0
Total Current Tax Expense (Benefit)	0	0	(1,000)
Deferred Tax Expense (Benefit)
Federal	60,000	66,000	54,000
Federal Investment Tax Credits	(6,000)	(6,000)	(4,000)
State	5,000	12,000	9,000
Total Deferred Tax Expense (Benefit)	59,000	72,000	59,000
Total Federal and State Income Tax Expense	$ 59,376	$ 71,719	$ 57,911