Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenue	$ 1,753.9	$ 1,742.0
OPERATING EXPENSES:
Salaries and related expenses	1,275.4	1,268.8
Office and general expenses	448.8	450.2
Total operating expenses	1,724.2	1,719.0
OPERATING INCOME	29.7	23.0
EXPENSES AND OTHER INCOME:
Interest expense	(20.9)	(22.6)
Interest income	5.2	5.8
Other income (expense), net	0.8	(19.2)
Total (expenses) and other income	(14.9)	(36.0)
Income (loss) before income taxes	14.8	(13.0)
Benefit of income taxes	(2.1)	(15.6)
Income of consolidated companies	16.9	2.6
Equity in net income of unconsolidated affiliates	1.2	0.1
NET INCOME	18.1	2.7
Net loss attributable to noncontrolling interests	3.4	2.7
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 21.5	$ 5.4
Earnings per share, Basic	$ 0.05	$ 0.01
Earnings per share, Diluted	$ 0.05	$ 0.01
Weighted-average number of common shares outstanding, Basic	391.7	400.6
Weighted-average number of common shares outstanding, Diluted	399.3	409.3
Dividends declared per common share	$ 0.18	$ 0.15