Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Statement [Abstract]
REVENUE	$ 7,014.6	$ 6,507.3	$ 6,007.4
OPERATING EXPENSES:
Salaries and related expenses	4,402.1	4,117.0	3,961.2
Office and general expenses	1,924.3	1,837.7	1,700.3
Restructuring and other reorganization-related charges, net	1.0	3.9	4.6
Total operating expenses	6,327.4	5,958.6	5,666.1
OPERATING INCOME	687.2	548.7	341.3
EXPENSES AND OTHER INCOME:
Interest expense	(136.8)	(139.7)	(155.6)
Interest income	37.8	28.7	35.0
Other income, net	150.2	12.9	11.7
Total (expenses) and other income	51.2	(98.1)	(108.9)
Income before income taxes	738.4	450.6	232.4
Provision for income taxes	190.2	171.3	90.1
Income of consolidated companies	548.2	279.3	142.3
Equity in net income of unconsolidated affiliates	3.3	1.9	1.1
NET INCOME	551.5	281.2	143.4
Net income attributable to noncontrolling interests	(19.2)	(20.1)	(22.1)
NET INCOME ATTRIBUTABLE TO IPG	532.3	261.1	121.3
Dividends on preferred stock	(11.6)	(15.6)	(27.6)
Benefit from preferred stock repurchased	0	25.7	0
Allocation to participating securities	0	0	(0.1)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 520.7	$ 271.2	$ 93.6
Earnings per share
Basic	$ 1.12	$ 0.57	$ 0.20
Diluted	$ 0.99	$ 0.47	$ 0.19
Weighted-average number of common shares outstanding:
Basic	465.5	473.6	468.2
Diluted	540.6	542.1	508.1
Dividends declared per common share	$ 0.24	$ 0.00	$ 0.00