SUPPLEMENTAL CASH FLOW (Non-Cash Transactions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Accrued Capital Expenditures	$ 29	$ 28	$ 29
Net Cost of Removal of Interim Retirements (1)	8	1	12
Commitment to Purchase Capital Lease Interests	36	0	109
Capital Lease Obligations (2)	0	0	1
Asset Retirement Obligations (3)	$ (1)	$ 3	$ 4