CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net Income	$ 70.4	$ 65.1	$ 171.8	$ 157.7
Other comprehensive income (loss):
Gain (loss) on cash flow hedges	7.0	(7.2)	2.5	(6.6)
Reclassification adjustment transferred to Net Income from cash flow hedges	1.0	0.1	1.1	0.5
Pension and other postretirement benefit costs	(1.9)	(1.8)	(3.6)	(3.5)
Total Comprehensive Income	76.5	56.2	171.8	148.1
Comprehensive loss attributable to noncontrolling interests	(0.1)	0	(0.1)	0
Comprehensive income attributable to controlling interests	$ 76.6	$ 56.2	$ 171.9	$ 148.1