Consolidated Statements of Stockholders' Equity (USD $) In Millions	Total USD ($)	Preferred Stock USD ($)	Common Stock, Shares	Common Stock USD ($)	Additional Paid-In Capital USD ($)	Retained Earnings USD ($)	Accumulated Other Comprehensive Loss, Net of Tax USD ($)	Treasury Stock USD ($)	Total IPG Stockholders' Equity USD ($)	Noncontrolling Interests USD ($)
Balance at Dec. 31, 2012	$ 2,456.6	$ 221.5		$ 48.8	$ 2,465.4	$ 738.3	$ (288.0)	$ (765.4)	$ 2,420.6	$ 36.0
Balance, Common Stock Shares at Dec. 31, 2012			492.0
Net income	76.8					74.8			74.8	2.0
Other comprehensive loss	(84.5)						(81.3)		(81.3)	(3.2)
Reclassifications related to redeemable noncontrolling interests	4.9									4.9
Distributions to noncontrolling interests	(10.4)									(10.4)
Change in redemption value of redeemable noncontrolling interests	0.6					0.6			0.6
Repurchase of common stock	(280.8)							(280.8)	(280.8)
Common stock dividends	(94.1)					(94.1)			(94.1)
Preferred stock dividends	(8.7)					(8.7)			(8.7)
Conversion of convertible notes to common stock, shares			16.9
Conversion of convertible notes to common stock	200.0			1.7	198.3				200.0
Capped call transaction	0				19.1			(19.1)	0
Stock-based compensation, shares			2.4
Stock-based compensation	37.6			0.4	37.2				37.6
Exercise of stock options, shares			4.7
Exercise of stock options	44.1			0.5	43.6				44.1
Shares withheld for taxes, shares			(1.5)
Shares withheld for taxes	(20.0)			(0.2)	(19.8)				(20.0)
Excess tax benefit from stock-based compensation	8.5				8.5				8.5
Other	2.9				1.8	(0.5)			1.3	(1.6)
Balance at Sep. 30, 2013	2,333.5	221.5		51.2	2,754.1	710.4	(369.3)	(1,065.3)	2,302.6	30.9
Balance, Common Stock Shares at Sep. 30, 2013			514.5
Balance at Dec. 31, 2013	2,250.8			53.0	2,975.2	864.5	(411.2)	(1,266.3)	2,215.2	35.6
Balance, Common Stock Shares at Dec. 31, 2013			532.3
Net income	174.1					168.2			168.2	5.9
Other comprehensive loss	(84.6)						(84.0)		(84.0)	(0.6)
Reclassifications related to redeemable noncontrolling interests	6.7									6.7
Distributions to noncontrolling interests	(13.9)									(13.9)
Change in redemption value of redeemable noncontrolling interests	3.0					3.0			3.0
Repurchase of common stock	(148.1)							(148.1)	(148.1)
Common stock dividends	(119.9)					(119.9)			(119.9)
Stock-based compensation, shares			3.3
Stock-based compensation	51.1			0.3	50.8				51.1
Exercise of stock options, shares			1.0
Exercise of stock options	12.0			0.1	11.9				12.0
Shares withheld for taxes, shares			(0.8)
Shares withheld for taxes	(14.8)			(0.1)	(14.7)				(14.8)
Excess tax benefit from stock-based compensation	4.9				4.9				4.9
Other	(5.4)				(3.7)	(0.6)			(4.3)	(1.1)
Balance at Sep. 30, 2014	$ 2,115.9			$ 53.3	$ 3,024.4	$ 915.2	$ (495.2)	$ (1,414.4)	$ 2,083.3	$ 32.6
Balance, Common Stock Shares at Sep. 30, 2014			535.8