Segment Information Schedule of Segment Reporting Information, by Segment (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

Summarized financial information concerning our reportable segments is shown in the following tables.

	Years ended December 31,
	2017			2016			2015
Revenue:
IAN	$	6,397.3		$	6,319.4		$	6,145.4
CMG	1,485.1			1,527.2			1,468.4
Total	$	7,882.4		$	7,846.6		$	7,613.8
Segment operating income (loss):
IAN	$	907.4		$	898.2		$	850.3
CMG	192.8			190.0			166.3
Corporate and other	(126.6		)	(147.2		)	(141.8		)
Total	973.6			941.0			874.8
Interest expense	(90.8		)	(90.6		)	(85.8		)
Interest income	19.4			20.1			22.8
Other expense, net	(26.2		)	(40.3		)	(49.6		)
Income before income taxes	$	876.0		$	830.2		$	762.2
Depreciation and amortization of property, equipment and intangible assets:
IAN	$	111.8		$	117.7		$	117.5
CMG	20.4			19.5			18.4
Corporate and other	24.9			23.0			21.1
Total	$	157.1		$	160.2		$	157.0
Capital expenditures:
IAN	$	112.0		$	149.2		$	117.5
CMG	17.7			16.6			12.7
Corporate and other	26.2			34.9			30.9
Total	$	155.9		$	200.7		$	161.1
	December 31,
	2017			2016
Total assets:
IAN	$	10,973.0		$	10,660.0
CMG	1,422.9			1,428.3
Corporate and other	299.3			396.9
Total	$	12,695.2		$	12,485.2