CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 47.3	$ 38.3	$ 214.0	$ 156.4
Other comprehensive income (loss):
Reclassification adjustment transferred to Net income from cash flow hedges	0.6	0.6	1.8	1.8
Pension and other postretirement benefit costs	0.6	0.0	2.3	(4.3)
Total Comprehensive Income	$ 48.5	$ 38.9	$ 218.1	$ 153.9