Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
REVENUE	$ 6,956.2	$ 7,014.6	$ 6,507.3
OPERATING EXPENSES:
Salaries and related expenses	4,391.9	4,402.1	4,117.0
Office and general expenses	1,886.0	1,925.3	1,841.6
Total operating expenses	6,277.9	6,327.4	5,958.6
OPERATING INCOME	678.3	687.2	548.7
EXPENSES AND OTHER INCOME:
Interest expense	(133.5)	(136.8)	(139.7)
Interest income	29.5	37.8	28.7
Other income, net	100.5	150.2	12.9
Total (expenses) and other income	(3.5)	51.2	(98.1)
Income before income taxes	674.8	738.4	450.6
Provision for income taxes	213.3	190.2	171.3
Income of consolidated companies	461.5	548.2	279.3
Equity in net income of unconsolidated affiliates	3.1	3.3	1.9
NET INCOME	464.6	551.5	281.2
Net income attributable to noncontrolling interests	(17.9)	(19.2)	(20.1)
NET INCOME ATTRIBUTABLE TO IPG	446.7	532.3	261.1
Dividends on preferred stock	(11.6)	(11.6)	(15.6)
Benefit from preferred stock repurchased	0	0	25.7
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 435.1	$ 520.7	$ 271.2
Earnings per share
Basic	$ 1.01	$ 1.12	$ 0.57
Diluted	$ 0.94	$ 0.99	$ 0.47
Weighted-average number of common shares outstanding:
Basic	432.5	465.5	473.6
Diluted	481.4	540.6	542.1
Dividends declared per common share	$ 0.24	$ 0.24	$ 0.00