Consolidated Statements of Operations (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income Statement [Abstract]
REVENUE	$ 1,740.7	$ 1,611.7	$ 3,215.5	$ 2,948.7
OPERATING EXPENSES:
Salaries and related expenses	1,095.7	991.0	2,175.8	1,970.3
Office and general expenses	470.8	442.9	910.0	859.7
Restructuring and other reorganization-related charges, net	0.2	0.6	1.0	0.9
Total operating expenses	1,566.7	1,434.5	3,086.8	2,830.9
OPERATING INCOME	174.0	177.2	128.7	117.8
EXPENSES AND OTHER INCOME:
Interest expense	(33.1)	(35.0)	(65.0)	(67.6)
Interest income	9.7	6.1	18.0	12.6
Other income (expense), net	5.3	(2.1)	(0.8)	(1.6)
Total (expenses) and other income	(18.1)	(31.0)	(47.8)	(56.6)
Income before income taxes	155.9	146.2	80.9	61.2
Provision for income taxes	47.6	63.3	26.1	48.0
Income of consolidated companies	108.3	82.9	54.8	13.2
Equity in net income (loss) of unconsolidated affiliates	0.6	0.2	0.9	(0.4)
NET INCOME	108.9	83.1	55.7	12.8
Net (income) loss attributable to noncontrolling interests	(4.3)	(0.6)	3.7	5.1
NET INCOME ATTRIBUTABLE TO IPG	104.6	82.5	59.4	17.9
Dividends on preferred stock	(2.9)	(2.9)	(5.8)	(9.8)
Benefit from preferred stock repurchased	0	25.7	0	25.7
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 101.7	$ 105.3	$ 53.6	$ 33.8
Earnings Per Share
Basic	$ 0.21	$ 0.22	$ 0.11	$ 0.07
Diluted	$ 0.19	$ 0.15	$ 0.11	$ 0.02
Weighted-average number of common shares outstanding:
Basic	473.1	473.0	474.6	472.1
Diluted	546.9	544.9	515.6	531.6
Dividends declared per common share	$ 0.06	$ 0.00	$ 0.12	$ 0.00