Segment Information Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Segments:
Assets	$ 12,336.7	$ 13,493.9
IAN
Segments:
Assets	10,602.4	11,035.3
CMG
Segments:
Assets	1,143.3	1,073.1
Corporate and other
Segments:
Assets	$ 591.0	$ 1,385.5