VARIABLE INTEREST ENTITIES (VIEs)- Consolidated VIEs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
ASSETS (LIABILITIES)
Cash and cash equivalents	$ 33	$ 33
Accounts receivable and other	48	42
Inventories	8	8
Other current assets	8	7
Equity investments	1,196	1,213
Property, plant and equipment	1,529	2,123
Other assets	6	3
Accounts payable and accrued liabilities	(36)	(31)
Provision for revenue sharing	(10)
Accounts payable to affiliates, net	(6)	(5)
Distributions payable		(1)
Accrued interest	(12)	(12)
Current portion of long-term debt	(36)	(51)
Long-term debt	(2,072)	(2,352)
Other liabilities	(29)	(29)
Consolidated VIEs | Restricted VIEs
ASSETS (LIABILITIES)
Cash and cash equivalents	16	19
Accounts receivable and other	39	30
Inventories	8	6
Other current assets	6	5
Equity investments	1,196	1,213
Property, plant and equipment	1,240	1,133
Other assets	1	1
Accounts payable and accrued liabilities	(33)	(24)
Accounts payable to affiliates, net	(40)	(42)
Distributions payable		(1)
Accrued interest	(2)	(2)
Current portion of long-term debt	(36)	(51)
Long-term debt	(341)	(308)
Other liabilities	(27)	(26)
Deferred state income tax	$ (9)	$ (10)