Segment Information Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Segments:
Assets	$ 12,218.3	$ 13,493.9
IAN
Segments:
Assets	10,597.1	11,035.3
CMG
Segments:
Assets	1,087.6	1,073.1
Corporate and other
Segments:
Assets	$ 533.6	$ 1,385.5