Earnings Per Share Basic and Diluted (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011		Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Net income available to IPG common stockholders - basic	$ 259.0	$ 208.1	[1]	$ 101.7	$ (48.1)	$ 195.0	$ 42.4	$ 105.3	$ (71.5)	$ 520.7	$ 271.2		$ 93.6
Net income available to IPG common stockholders - diluted										537.8	254.9		95.0
Weighted-average number of common shares outstanding - basic										465.5	473.6		468.2
Weighted-average number of common shares outstanding - diluted										540.6	542.1		508.1
Earnings per share available to IPG common stockholders - basic	$ 0.58	$ 0.45		$ 0.21	$ (0.10)	$ 0.41	$ 0.09	$ 0.22	$ (0.15)	$ 1.12	$ 0.57		$ 0.20
Earnings per share available to IPG common stockholders - diluted	$ 0.50	$ 0.40		$ 0.19	$ (0.10)	$ 0.36	$ 0.08	$ 0.15	$ (0.15)	$ 0.99	$ 0.47		$ 0.19
Adjustments: Effect of dilutive securities
Preferred stock dividends										11.6	0		0
Benefit from preferred stock repurchased										0	(21.7)	[2]	0
Add: Effect of dilutive securities
Restricted stock, stock options and other equity awards										9.1	11.3		7.7
Preferred stock outstanding										16.5	0		0
Preferred stock repurchased										0	8.9		0
Dividends declared and associated with preferred stock repurchased											4.0
4.25% Notes
Adjustments: Effect of dilutive securities
Interest on convertible debt										1.4	1.4		1.4
Add: Effect of dilutive securities
Convertible debt securities										33.0	32.2		32.2
Stated Interest Rate	4.25%									4.25%
4.75% Notes
Adjustments: Effect of dilutive securities
Interest on convertible debt										$ 4.1	$ 4.0		$ 0
Add: Effect of dilutive securities
Convertible debt securities										16.5	16.1		0
Stated Interest Rate	4.75%									4.75%
4.50% Notes
Add: Effect of dilutive securities
Stated Interest Rate	4.50%									4.50%
Debt Maturity Date										Mar. 15, 2023

[1] The three months ended September 30, 2011, includes a pre-tax gain of $132.2 related to the sale of approximately half of our holdings in Facebook, Inc.

[2] For the year ended December 31, 2010, the benefit from the preferred stock repurchased is excluded from net income available to IPG common stockholders for purposes of calculating diluted earnings per share since the associated common shares, if converted, were dilutive. In addition, the benefit is also net of $4.0 of preferred dividends that were declared during the first quarter of 2010 and associated with the preferred stock repurchased.