REGULATORY MATTERS (Tables)

9 Months Ended

Sep. 30, 2015

REGULATORY MATTERS [Abstract]

Schedule of Changes in Net Regulatory Asset Balance

	For the three months						For the nine months
	ended September 30,						ended September 30,
	2015			2014			2015			2014
	(in millions)
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	)