Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
REVENUE	$ 7,122.3	$ 6,956.2	$ 7,014.6
OPERATING EXPENSES:
Salaries and related expenses	4,545.5	4,391.9	4,402.1
Office and general expenses	1,917.9	1,887.2	1,924.3
Restructuring and other reorganization-related charges (reversals), net	60.6	(1.2)	1.0
Total operating expenses	6,524.0	6,277.9	6,327.4
OPERATING INCOME	598.3	678.3	687.2
EXPENSES AND OTHER INCOME:
Interest expense	(122.7)	(133.5)	(136.8)
Interest income	24.7	29.5	37.8
Other (expense) income, net	(32.3)	100.5	150.2
Total (expenses) and other income	(130.3)	(3.5)	51.2
Income before income taxes	468.0	674.8	738.4
Provision for income taxes	181.2	213.3	190.2
Income of consolidated companies	286.8	461.5	548.2
Equity in net income of unconsolidated affiliates	2.1	3.1	3.3
NET INCOME	288.9	464.6	551.5
Net income attributable to noncontrolling interests	(21.0)	(17.9)	(19.2)
NET INCOME ATTRIBUTABLE TO IPG	267.9	446.7	532.3
Dividends on preferred stock	(8.7)	(11.6)	(11.6)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 259.2	$ 435.1	$ 520.7
Earnings per share available to IPG common stockholders:
Basic	$ 0.62	$ 1.01	$ 1.12
Diluted	$ 0.61	$ 0.94	$ 0.99
Weighted-average number of common shares outstanding:
Basic	421.1	432.5	465.5
Diluted	429.6	481.4	540.6
Dividends declared per common share	$ 0.30	$ 0.24	$ 0.24