Interest Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Interest Expense
Interest on borrowings	$ 28.0	$ 28.0	$ 84.1	$ 85.8
Fees on financing agreements	3.3	5.8	28.4	34.2
Interest capitalized and other	(2.6)	(1.7)	(7.6)	(5.0)
Total interest expense	28.7	32.1	104.9	115.0
Accelerated amortization of debt issuance costs			$ 15.2	$ 19.9