Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
REVENUE	$ 7,613.8	$ 7,537.1	$ 7,122.3
OPERATING EXPENSES:
Salaries and related expenses	4,857.7	4,820.4	4,545.5
Office and general expenses	1,885.0	1,928.1	1,917.9
Restructuring and other reorganization-related (reversals) charges, net	(0.8)	0.2	60.6
Total operating expenses	6,741.9	6,748.7	6,524.0
OPERATING INCOME	871.9	788.4	598.3
EXPENSES AND OTHER INCOME:
Interest expense	(85.8)	(84.9)	(122.7)
Interest income	22.8	27.4	24.7
Other expense, net	(46.7)	(10.2)	(32.3)
Total (expenses) and other income	(109.7)	(67.7)	(130.3)
Income before income taxes	762.2	720.7	468.0
Provision for income taxes	282.8	216.5	181.2
Income of consolidated companies	479.4	504.2	286.8
Equity in net income of unconsolidated affiliates	1.1	1.2	2.1
NET INCOME	480.5	505.4	288.9
Net income attributable to noncontrolling interests	(25.9)	(28.3)	(21.0)
NET INCOME ATTRIBUTABLE TO IPG	454.6	477.1	267.9
Dividends on preferred stock	0.0	0.0	(8.7)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 454.6	$ 477.1	$ 259.2
Earnings per share available to IPG common stockholders:
Basic	$ 1.11	$ 1.14	$ 0.62
Diluted	$ 1.09	$ 1.12	$ 0.61
Weighted-average number of common shares outstanding:
Basic	408.1	419.2	421.1
Diluted	415.7	425.4	429.6
Dividends declared per common share	$ 0.48	$ 0.38	$ 0.30