Consolidated Statements of Operations (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Income Statement [Abstract]
REVENUE	$ 1,726.5	$ 1,553.4	$ 4,942.0	$ 4,502.1
OPERATING EXPENSES:
Salaries and related expenses	1,088.0	1,007.1	3,263.8	2,977.4
Office and general expenses	465.5	444.7	1,375.5	1,304.4
Restructuring and other reorganization-related (reversals) charges, net	(0.2)	1.4	0.8	2.3
Total operating expenses	1,553.3	1,453.2	4,640.1	4,284.1
OPERATING INCOME	173.2	100.2	301.9	218.0
EXPENSES AND OTHER INCOME:
Interest expense	(32.9)	(34.7)	(97.9)	(102.3)
Interest income	9.7	6.8	27.7	19.4
Other income (expense), net	137.1	(3.1)	136.3	(4.7)
Total (expenses) and other income	113.9	(31.0)	66.1	(87.6)
Income before income taxes	287.1	69.2	368.0	130.4
Provision for income taxes	70.4	24.4	96.5	72.4
Income of consolidated companies	216.7	44.8	271.5	58.0
Equity in net income of unconsolidated affiliates	0.8	0.8	1.7	0.4
NET INCOME	217.5	45.6	273.2	58.4
Net (income) loss attributable to noncontrolling interests	(6.5)	(0.3)	(2.8)	4.8
NET INCOME ATTRIBUTABLE TO IPG	211.0	45.3	270.4	63.2
Dividends on preferred stock	(2.9)	(2.9)	(8.7)	(12.7)
Benefit from preferred stock repurchased	0	0	0	25.7
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 208.1	$ 42.4	$ 261.7	$ 76.2
Earnings per share
Basic	$ 0.45	$ 0.09	$ 0.56	$ 0.16
Diluted	$ 0.40	$ 0.08	$ 0.50	$ 0.11
Weighted-average number of common shares outstanding:
Basic	464.7	474.7	471.3	473.0
Diluted	537.6	533.6	527.8	526.4
Dividends declared per common share	$ 0.06	$ 0.00	$ 0.18	$ 0.00