Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Summary of Significant Accounting Policies [Abstract]
Customer surcharges	$ 28.8	$ 26.1	$ 58.5	$ 54.2
Number of reportable segments	1		1