Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Earnings Per Share [Abstract]
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 99.4		$ 79.9		$ 78.5		$ 20.7
Net income available to IPG common stockholders - diluted	99.4		82.8		78.5		20.7
Weighted Average Number of Shares Outstanding, Basic	421.1		425.1		421.9		419.7
Weighted Average Number of Shares Outstanding, Diluted	428.1		448.3		428.5		425.1
Earnings per share available to IPG common stockholders - basic	$ 0.24		$ 0.19		$ 0.19		$ 0.05
Earnings per share available to IPG common stockholders - diluted	$ 0.23		$ 0.18		$ 0.18		$ 0.05
Preferred stock dividends, Effect of dilutive securities	$ 0	[1]	$ 2.9	[1]	$ 0	[1]	$ 0	[1]
Restricted stock, stock options and other equity awards, Effect of dilutive securities, Incremental common shares	7.0		6.1		6.6		5.4
Preferred stock outstanding, Effect of dilutive securities, Incremental common shares	0	[1]	17.1	[1]	0	[1]	0	[1]

[1] We converted all of our 5 1/4% Series B Cumulative Convertible Perpetual Preferred Stock (the "Series B Preferred Stock") into common stock in October 2013.