REGULATORY MATTERS Net Changes in Regulatory Assets and Liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)
Revenue Accruals and Deferrals
Beginning balance	$ (1)
Net collection of 2015 revenue deferrals and accruals, including accrued interest	(8)
Net revenue accrual for the six months ended June 30, 2017	15
Ending balance	$ 6