Related Parties (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			12 Months Ended
	Dec. 31, 2011 City Deal [Member]	Dec. 31, 2010 City Deal [Member]	Dec. 31, 2012 City Deal [Member]	Dec. 31, 2012 InnerWorkings [Member]	Dec. 31, 2012 Echo Global Logistics [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	$ 1.3		$ 0	$ 1.3
Related Party Transaction, Expenses from Transactions with Related Party	1.4			1.1	1.9
Related Party Transaction, Reduction to Revenue	$ 2.4	$ 1.1