CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Other comprehensive income (loss), tax
Tax expense (benefit) on gains (losses) on changes in unrealized fair value of derivatives designated as cash flow hedges		$ (12.2)		$ (24.1)
Pension and other postretirement plans adjustments:
Tax expense (benefit) on net unamortized gain (loss) incurred	0.1	0.3	0.2	0.5
Tax expense (benefit) on prior service cost incurred	$ 0.5	$ 0.5	$ 1.0	$ 1.0