CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Settlements tax	$ (18.5)	$ (76.7)	$ (50.0)	$ (140.4)
Ineffectiveness tax	0.8	1.1	0.3	(1.0)
Change in fair value of derivative instruments tax	45.0	(23.7)	14.7	84.8
Amortization of prior service cost included in net periodic pension cost tax	$ 0.2	$ 0.1	$ 0.4	$ 0.3