Segment Information Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segments:
Revenue	$ 1,841.1	$ 1,700.4	$ 5,330.0	$ 4,999.6
Operating Income (Loss)	171.3	141.5	355.4	273.9
Interest expense	20.7	23.7	63.5	98.0
Interest income	(7.5)	(5.8)	(20.3)	(18.0)
Total other expense, net	0.6	46.6	10.1	40.0
Income before income taxes	157.5	77.0	302.1	153.9
Depreciation and amortization of fixed assets and intangible assets	41.0	40.5	121.7	117.9
Capital expenditures	35.7	44.8	94.4	91.6
Assets	11,778.4		11,778.4		12,905.0
IAN
Segments:
Revenue	1,464.6	1,370.9	4,276.3	4,047.7
Operating Income (Loss)	165.5	119.9	361.0	266.5
Depreciation and amortization of fixed assets and intangible assets	31.0	32.9	92.7	95.4
Capital expenditures	20.9	24.5	52.0	48.0
Assets	10,689.4		10,689.4		11,425.1
CMG
Segments:
Revenue	376.5	329.5	1,053.7	951.9
Operating Income (Loss)	47.0	39.7	105.8	88.3
Depreciation and amortization of fixed assets and intangible assets	4.9	3.9	13.7	11.6
Capital expenditures	2.6	2.4	8.2	6.5
Assets	1,311.5		1,311.5		1,203.8
Corporate and Other
Segments:
Operating Income (Loss)	(41.2)	(18.1)	(111.4)	(80.9)
Depreciation and amortization of fixed assets and intangible assets	5.1	3.7	15.3	10.9
Capital expenditures	12.2	17.9	34.2	37.1
Assets	$ (222.5)		$ (222.5)		$ 276.1