CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Net Income	$ 59.0	$ 47.2	$ 216.7	$ 145.4
Other comprehensive income (loss):
(Loss) gain on cash flow hedges	0.6	(1.5)	7.2	(2.9)
Reclassification adjustment transferred to Net Income from cash flow hedges	(0.6)	0.2	(1.1)	(0.7)
Pension and other postretirement benefit costs	(1.8)	(1.5)	(5.3)	(4.5)
Total Comprehensive Income	$ 57.2	$ 47.0	$ 205.3	$ 144.5