Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Revenue	$ 1,742.0	$ 1,676.0
OPERATING EXPENSES:
Salaries and related expenses	1,270.9	1,215.2
Office and general expenses	450.2	453.0
Total operating expenses	1,721.1	1,668.2
OPERATING INCOME	20.9	7.8
EXPENSES AND OTHER INCOME:
Interest expense	(22.6)	(20.9)
Interest income	5.8	7.2
Other (expense) income, net	(17.1)	0.3
Total (expenses) and other income	(33.9)	(13.4)
Loss before income taxes	(13.0)	(5.6)
Benefit of income taxes	(15.6)	(1.4)
Income (loss) of consolidated companies	2.6	(4.2)
Equity in net income of unconsolidated affiliates	0.1	0.0
NET INCOME (LOSS)	2.7	(4.2)
Net loss attributable to noncontrolling interests	2.7	2.4
NET INCOME (LOSS) AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 5.4	$ (1.8)
Earnings per share, Basic	$ 0.01	$ 0.00
Earnings per share, Diluted	$ 0.01	$ 0.00
Weighted-average number of common shares outstanding, Basic	400.6
Weighted-average number of common shares outstanding, Diluted	409.3
Weighted Average Number of Shares Outstanding, Basic and Diluted		411.1
Dividends declared per common share	$ 0.150	$ 0.120