QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2013

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

(Millions)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total
2013
Operating revenues	$	433.4	$	367.8	$	371.9	$	406.2	$	1,579.3
Operating income	77.4		46.9		65.2		50.5		240.0
Net income attributed to common shareholder	44.6		25.9		37.0		27.3		$	134.8
2012
Operating revenues	$	404.2	$	337.5	$	378.1	$	379.4	$	1,499.2
Operating income	72.0		41.8		64.3		46.1		224.2
Net income attributed to common shareholder	42.1		22.6		42.5		24.5		131.7