Acquisitions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Business Combinations
Number of completed acquisitions	11		12		22
Business Combination, Recognized Identifiable Goodwill and Liabilities Acquired, Net	$ 97.0		$ 201.0
Goodwill, Purchase Accounting Adjustments	0	[1]	2.2	[1]	133.0
IAN
Business Combinations
Number of completed acquisitions	9		8		18
CMG
Business Combinations
Number of completed acquisitions	2		4		4
Goodwill, Purchase Accounting Adjustments	$ 0	[1]	$ 0	[1]

[1] For all periods presented we have not recorded a goodwill impairment charge.