SUBSEQUENT EVENTS (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended
	Aug. 31, 2012	Jul. 31, 2012	Aug. 01, 2012
Great Lakes
Subsequent events
Aggregate distribution declared and payable by investee		$ 23
Ownership interest (as a percent)			46.45%
Partnership's share of distributions declared and payable by investee	11
Northern Border
Subsequent events
Aggregate distribution declared and payable by investee		40
Ownership interest (as a percent)			50.00%
Partnership's share of distributions declared and payable by investee	20
GTN
Subsequent events
Aggregate distribution declared and payable by investee		29
Ownership interest (as a percent)			25.00%
Partnership's share of distributions declared and payable by investee	7
Bison
Subsequent events
Aggregate distribution declared and payable by investee		16
Ownership interest (as a percent)			25.00%
Partnership's share of distributions declared and payable by investee	$ 4
Cash distribution declared
Subsequent events
Cash distribution (in dollars per unit)		$ 0.78