SUBSEQUENT EVENTS (Details) (USD $) In Millions, except Per Share data, unless otherwise specified					0 Months Ended
	Mar. 31, 2013 Great Lakes	Mar. 31, 2013 Northern Border	Mar. 31, 2013 GTN	Mar. 31, 2013 Bison	Apr. 23, 2013 Subsequent event Cash distribution declared	Apr. 18, 2013 Subsequent event Cash distribution declared Great Lakes	Apr. 18, 2013 Subsequent event Cash distribution declared Northern Border	Apr. 18, 2013 Subsequent event Cash distribution declared GTN	Apr. 18, 2013 Subsequent event Cash distribution declared Bison	May 02, 2013 Subsequent event Cash Distribution Paid Great Lakes Expected	May 02, 2013 Subsequent event Cash Distribution Paid Northern Border Expected	May 02, 2013 Subsequent event Cash Distribution Paid GTN Expected	May 02, 2013 Subsequent event Cash Distribution Paid Bison Expected
Subsequent events
Cash distribution (in dollars per unit)					$ 0.78
Aggregate distribution declared and payable by investee						$ 12	$ 44	$ 33	$ 13
Ownership interest (as a percent)	46.45%	50.00%	25.00%	25.00%						46.45%	50.00%	25.00%	25.00%
Partnership's share of distributions declared and payable by investee										$ 6	$ 22	$ 8	$ 3