TRANSACTIONS WITH MAJOR CUSTOMERS (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Transactions with major customers
Revenues	$ 91	$ 91	$ 89	$ 86	$ 89	$ 83	$ 85	$ 87	$ 357	$ 344	$ 336
Trade accounts receivable	34				32				34	32
Total revenues | Customer concentration risk | Anadarko Energy Services Company
Transactions with major customers
Revenues									48	48	48
Total revenues | Customer concentration risk | Pacific Gas and Electric Company
Transactions with major customers
Revenues									36	42	$ 45
Accounts receivable and other | Amounts owed by major customers | Anadarko Energy Services Company
Transactions with major customers
Trade accounts receivable	$ 4				4				$ 4	4
Accounts receivable and other | Amounts owed by major customers | Pacific Gas and Electric Company
Transactions with major customers
Trade accounts receivable					$ 3					$ 3