Segment Information Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segments:
Revenue	$ 1,917.9	$ 1,876.1	$ 3,659.9	$ 3,552.1
OPERATING INCOME	224.8	215.8	245.7	223.6
Interest expense	(24.5)	(20.3)	(47.1)	(41.2)
Interest income	5.6	5.0	11.4	12.2
Other (expense) income, net	(0.1)	0.5	(17.2)	0.8
Income before income taxes	205.8	201.0	192.8	195.4
Depreciation and amortization of fixed assets and intangible assets	39.8	39.5	77.8	78.2
Capital expenditures	36.0	29.6	63.0	49.8
IAN
Segments:
Revenue	1,548.5	1,522.1	2,950.1	2,867.2
OPERATING INCOME	195.7	204.9	235.4	236.3
Depreciation and amortization of fixed assets and intangible assets	29.2	30.1	56.8	59.5
Capital expenditures	26.9	20.4	47.2	32.5
CMG
Segments:
Revenue	369.4	354.0	709.8	684.9
OPERATING INCOME	50.0	41.4	70.4	61.3
Depreciation and amortization of fixed assets and intangible assets	4.9	4.5	9.7	9.1
Capital expenditures	2.2	2.3	3.7	3.4
Corporate and Other
Segments:
OPERATING INCOME	(20.9)	(30.5)	(60.1)	(74.0)
Depreciation and amortization of fixed assets and intangible assets	5.7	4.9	11.3	9.6
Capital expenditures	$ 6.9	$ 6.9	$ 12.1	$ 13.9