REGULATORY MATTERS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Net regulatory asset balance at beginning of period	$ 2.0	$ (1.2)	$ 6.0	$ 7.7
Current period (over)/under recovery revenue adjustments	24.0	(4.4)	24.5	(5.6)
Amortization of prior year regulatory asset	(0.8)		(5.3)	(7.7)
Net regulatory asset (liability) balance at end of period	25.2	(5.6)	25.2	(5.6)
Allowance for equity used during construction	13.7	14.5	54.0	47.8
Southern Access Pipeline [Member]
Amortization through revenue		1.7		6.1
Alberta Clipper Pipeline [Member]
Property tax over recovery liabilities.	1.6		1.6		$ 5.9
Amortization through revenue	$ 1.1	$ 1.7	$ 4.0	$ 5.2
Obligation to refund overcollection to customers (in percentage)			50.00%