Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Income Statement [Abstract]
REVENUE	$ 1,715.7	$ 1,740.7	$ 3,222.5	$ 3,215.5
OPERATING EXPENSES:
Salaries and related expenses	1,088.9	1,095.7	2,193.8	2,175.8
Office and general expenses	450.4	471.0	891.7	911.0
Total operating expenses	1,539.3	1,566.7	3,085.5	3,086.8
OPERATING INCOME	176.4	174.0	137.0	128.7
EXPENSES AND OTHER INCOME:
Interest expense	(32.7)	(33.1)	(65.3)	(65.0)
Interest income	6.7	9.7	14.7	18.0
Other income (expense), net	4.7	5.3	3.4	(0.8)
Total (expenses) and other income	(21.3)	(18.1)	(47.2)	(47.8)
Income before income taxes	155.1	155.9	89.8	80.9
Provision for income taxes	50.1	47.6	30.9	26.1
Income of consolidated companies	105.0	108.3	58.9	54.8
Equity in net income of unconsolidated affiliates	0.5	0.6	0.9	0.9
NET INCOME	105.5	108.9	59.8	55.7
Net (income) loss attributable to noncontrolling interests	(3.6)	(4.3)	(0.9)	3.7
NET INCOME ATTRIBUTABLE TO IPG	101.9	104.6	58.9	59.4
Dividends on preferred stock	(2.9)	(2.9)	(5.8)	(5.8)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 99.0	$ 101.7	$ 53.1	$ 53.6
Earnings per share available to IPG common stockholders:
Basic	$ 0.23	$ 0.21	$ 0.12	$ 0.11
Diluted	$ 0.22	$ 0.19	$ 0.12	$ 0.11
Weighted-average number of common shares outstanding:
Basic	437.4	473.1	437.5	474.6
Diluted	477.7	546.9	459.7	515.6
Dividends declared per common share	$ 0.06	$ 0.06	$ 0.12	$ 0.12