INCOME TAXES (Additional Information) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Increase in income tax expense due to change in tax rate	$ 7,000,000
Increase in regulated liabilities due to change in tax rate	343,000,000
Decrease deferred tax liabilities due to change in tax rate	(336,000,000)
Unrecognized tax benefits, if recognized, decrease in income tax expense (benefit)	1,000,000	$ 1,000,000
Interest expense related to uncertain tax position	0	0	$ 0
Interest payable	0	0
Penalties accrued	$ 0	$ 0