SUBSEQUENT EVENTS (Details) (USD $) In Millions, except Per Share data, unless otherwise specified			3 Months Ended		0 Months Ended
	Jun. 30, 2014 Northern Border	Jun. 30, 2014 Great Lakes	Jun. 30, 2014 GTN	Jun. 30, 2014 Bison	Jul. 23, 2014 Subsequent event	Aug. 01, 2014 Subsequent event GTN Expected	Aug. 01, 2014 Subsequent event Bison Expected	Jul. 08, 2014 Subsequent event GTN	Jul. 08, 2014 Subsequent event Bison	Jul. 16, 2014 Subsequent event Distribution declared Northern Border	Jul. 08, 2014 Subsequent event Distribution declared Great Lakes	Aug. 01, 2014 Subsequent event Cash Distribution Paid Northern Border Expected	Aug. 01, 2014 Subsequent event Cash Distribution Paid Great Lakes Expected
Subsequent events
Cash distribution (in dollars per unit)					$ 0.84
Distribution declared								$ 28	$ 17
Partnership interest (as a percent)			70.00%	70.00%
Distribution received by Partnership						20	12
Partnership distribution										42	10
Ownership interest (as a percent)	50.00%	46.45%
Partnership's share of distributions												$ 21	$ 5