INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			0 Months Ended	3 Months Ended			9 Months Ended			0 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 27, 2013 Great Lakes	Sep. 30, 2013 Great Lakes	Mar. 31, 2013 Great Lakes	Sep. 30, 2012 Great Lakes	Sep. 30, 2013 Great Lakes	Sep. 30, 2012 Great Lakes	Dec. 31, 2012 Great Lakes	Jan. 02, 2013 Northern Border	Sep. 30, 2013 Northern Border	Sep. 30, 2012 Northern Border	Sep. 30, 2013 Northern Border	Sep. 30, 2012 Northern Border	Dec. 31, 2012 Northern Border	Apr. 30, 2006 Northern Border
Investments in unconsolidated affiliates
Ownership interest at the end of the period (as a percent)							46.45%			46.45%				50.00%		50.00%
Equity Earnings/(Losses) from Unconsolidated Affiliates	$ 15	$ 24	$ 48	$ 77			$ (2)		$ 6		$ 23			$ 17	$ 18	$ 48	$ 54
Undistributed earnings										0	0					0	0
Investments in Unconsolidated Affiliates	1,161		1,161		1,189		666			666		677		495		495		512
Amortization period of transaction fee																12 years
Transaction fee																10
Additional ownership interest acquired (as a percent)																			20.00%
Increase in transportation rates compared to current rates (as a percent)						21.00%
Equity contribution								4		4	4
Total cash call issued to fund debt repayment								9
Assets
Current assets							37			37		56
Cash and cash equivalents														29		29		28
Other current assets														33		33		35
Plant, property and equipment, net							777			777		799		1,205		1,205		1,234
Other assets														31		31		31
Assets, total							814			814		855		1,298		1,298		1,328
LIABILITIES AND PARTNERS' EQUITY
Current liabilities							21			21		30		54		54		53
Deferred credits and other														19		19		16
Long-term debt, including current maturities							345			345		354		473		473		473
Partners' equity
Partners' equity							448			448		471		754		754		789
Accumulated other comprehensive loss														(2)		(2)		(3)
Liabilities and Equity, total							814			814		855		1,298		1,298		1,328
Revenues (expenses)
Transmission revenues							26		46	90	143			72	78	213	232
Operating expenses							(15)		(17)	(45)	(48)			(18)	(21)	(56)	(57)
Depreciation							(8)		(8)	(24)	(24)			(15)	(16)	(44)	(48)
Financial charges and other							(6)		(7)	(20)	(21)			(6)	(5)	(17)	(18)
Net income/(loss)							$ (3)		$ 14	$ 1	$ 50			$ 33	$ 36	$ 96	$ 109
Reduction in current transportation rates (as a percent)													11.00%