Interest Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest Expense
Interest on borrowings	$ 43.8	$ 28.0	$ 106.8	$ 84.1
Fees on financing agreements	3.9	3.3	11.4	28.4
Interest on tax liabilities	0.5		12.2	1.0
Interest capitalized and other	(7.2)	(2.6)	(18.0)	(8.6)
Total interest expense	$ 41.0	$ 28.7	$ 112.4	$ 104.9