VARIABLE INTEREST ENTITIES - Consolidated VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
ASSETS (LIABILITIES)
Cash and cash equivalents	$ 45	$ 33
Accounts receivable and other	33	48
Inventories	9	8
Other current assets	3	8
Equity investments	1,118	1,196
Property, plant and equipment, net	1,520	1,529
Other assets		6
Accounts payable and accrued liabilities	(26)	(36)
Accounts payable to affiliates, net	(6)	(6)
Accrued interest	(11)	(12)
Current portion of long-term debt	(101)	(36)
Long-term debt	(1,892)	(2,072)
Other liabilities	(34)	(29)
Consolidated VIEs | Restricted VIEs
ASSETS (LIABILITIES)
Cash and cash equivalents	14	16
Accounts receivable and other	29	39
Inventories	9	8
Other current assets	3	6
Equity investments	1,118	1,196
Property, plant and equipment, net	1,240	1,240
Other assets	1	1
Accounts payable and accrued liabilities	(22)	(33)
Accounts payable to affiliates, net	(87)	(40)
Accrued interest	(2)	(2)
Current portion of long-term debt	(101)	(36)
Long-term debt	(251)	(341)
Other liabilities	(28)	(27)
Deferred state income tax	$ (9)	$ (9)