Segment Information Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segments:
Revenue	$ 1,700.4	$ 1,670.4	$ 4,999.6	$ 4,892.9
Operating income (loss)	141.5	131.4	273.9	268.4
Interest expense	(23.7)	(31.6)	(98.0)	(96.9)
Interest income	5.8	6.7	18.0	21.4
Other (expense) income, net	(46.6)	1.7	(40.0)	5.1
Income before income taxes	77.0	108.2	153.9	198.0
Depreciation and amortization of fixed assets and intangible assets	40.5	37.4	117.9	108.8
Capital expenditures	44.8	41.1	91.6	99.3
IAN
Segments:
Revenue	1,370.9	1,332.5	4,047.7	3,999.7
Operating income (loss)	119.9	116.6	266.5	278.6
Depreciation and amortization of fixed assets and intangible assets	32.9	30.1	95.4	88.4
Capital expenditures	24.5	19.9	48.0	52.6
CMG
Segments:
Revenue	329.5	337.9	951.9	893.2
Operating income (loss)	39.7	34.4	88.3	73.1
Depreciation and amortization of fixed assets and intangible assets	3.9	3.9	11.6	10.6
Capital expenditures	2.4	11.9	6.5	17.5
Corporate and Other
Segments:
Operating income (loss)	(18.1)	(19.6)	(80.9)	(83.3)
Depreciation and amortization of fixed assets and intangible assets	3.7	3.4	10.9	9.8
Capital expenditures	$ 17.9	$ 9.3	$ 37.1	$ 29.2