Segment Information Operations (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segments:
Revenue	$ 1,740.7	$ 1,611.7	$ 3,215.5	$ 2,948.7
Segment operating income	174.2	177.8	129.7	118.7
Restructuring and other reorganization-related charges, net	(0.2)	(0.6)	(1.0)	(0.9)
Interest expense	(33.1)	(35.0)	(65.0)	(67.6)
Interest income	9.7	6.1	18.0	12.6
Other income (expense), net	5.3	(2.1)	(0.8)	(1.6)
Income before income taxes	155.9	146.2	80.9	61.2
Depreciation and amortization of fixed assets and intangible assets	37.7	36.8	73.3	74.2
Capital expenditures	36.2	18.9	53.1	28.3
IAN
Segments:
Segment revenue	1,471.7	1,363.2	2,707.6	2,472.4
Segment operating income	184.7	190.0	163.3	156.7
Depreciation and amortization of fixed assets and intangible assets	31.4	28.6	60.7	57.3
Capital expenditures	22.8	15.7	36.8	24.3
CMG
Segments:
Segment revenue	269.0	248.5	507.9	476.3
Segment operating income	28.0	21.8	38.7	29.5
Depreciation and amortization of fixed assets and intangible assets	3.3	3.4	6.4	7.0
Capital expenditures	2.9	1.6	4.2	1.9
Corporate and Other
Segments:
Segment operating income	(38.5)	(34.0)	(72.3)	(67.5)
Depreciation and amortization of fixed assets and intangible assets	3.0	4.8	6.2	9.9
Capital expenditures	$ 10.5	$ 1.6	$ 12.1	$ 2.1