VARIABLE INTEREST ENTITIES - Consolidated VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	[1]	Dec. 31, 2014	[1]
ASSETS (LIABILITIES)
Cash and cash equivalents	$ 33	$ 64	[1]	$ 55		$ 153
Accounts receivable and other	42	47	[1]
Inventories	8	7	[1],[2]
Other current assets	7	7	[1],[2]
Equity investments	1,213	918	[1]
Plant, property and equipment	2,123	2,180	[1]
Other assets	3	1	[1],[2]
Accounts payable and accrued liabilities	(31)	(29)	[1],[2]
Accounts payable to affiliates, net	(5)	(8)	[1],[2]
Distributions payable	(1)	(3)	[1],[2]
Accrued interest	(12)	(10)	[1],[2]
Current portion of long-term debt	(51)	(52)	[1]
Long-term debt	(2,352)	(1,859)	[1]
Other liabilities	(29)	(28)	[1]
Consolidated VIEs | Restricted VIEs
ASSETS (LIABILITIES)
Cash and cash equivalents	19	14
Accounts receivable and other	30	33
Inventories	6	6
Other current assets	5	6
Equity investments	1,213	918
Plant, property and equipment	1,133	1,146
Other assets	1	2
Accounts payable and accrued liabilities	(24)	(21)
Accounts payable to affiliates, net	(42)	(32)
Distributions payable	(1)	(3)
Accrued interest	(2)	(2)
Current portion of long-term debt	(51)	(52)
Long-term debt	(308)	(337)
Other liabilities	(26)	(25)
Deferred state income tax	$ (10)	$ (10)

[1] Recast to consolidate PNGTS (Refer to Notes 2 and 7).

[2] Recast to consolidate PNGTS (Refer to Notes 2 and 7).