Consolidated Statements of Stockholders' Equity (USD $) In Millions	Total USD ($)	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, 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 loss	(22.4)				(20.9)
Income (Loss) Attributable to Parent								(20.9)
Net Income (Loss) Attributable to Noncontrolling Interest	(1.5)								(1.5)
Other comprehensive loss	(0.3)					0.3		0.3
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	(2.1)								(0.6)
Reclassifications related to redeemable noncontrolling interests	4.5								4.5
Distributions to noncontrolling interests	(5.7)								(5.7)
Change in redemption value of redeemable noncontrolling interests	1.9				1.9			1.9
Repurchase of common stock	(44.9)						(44.9)	(44.9)
Common stock dividends	(40.2)				(40.2)			(40.2)
Stock-based compensation, shares		3.1
Stock-based compensation, value	32.8		0.2	32.6				32.8
Exercise of stock options, shares		0.5
Exercise of stock options, value	6.3		0.1	6.2				6.3
Shares withheld for taxes, shares		(0.8)
Shares withheld for taxes, value	(14.6)		(0.1)	(14.5)				(14.6)
Excess tax benefit from stock-based compensation	3.3			3.3				3.3
Other	(0.2)			(0.1)	(0.3)			(0.4)	(0.2)
Balance at Mar. 31, 2014	2,171.3		53.2	3,002.7	805.0	(410.9)	(1,311.2)	2,138.8	32.5
Balance, Common Stock Shares at Mar. 31, 2014		535.1
Balance at Dec. 31, 2014	2,151.2		41.2	1,547.5	1,183.3	(636.7)	(19.0)	2,116.3	34.9
Balance, Common Stock Shares at Dec. 31, 2014		414.6
Net loss	(4.2)				(1.8)
Income (Loss) Attributable to Parent								(1.8)
Net Income (Loss) Attributable to Noncontrolling Interest	(2.4)								(2.4)
Other comprehensive loss	(128.8)					(128.0)		(128.0)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	(3.2)								(0.8)
Reclassifications related to redeemable noncontrolling interests	1.5								1.5
Distributions to noncontrolling interests	(1.2)								(1.2)
Change in redemption value of redeemable noncontrolling interests	(5.8)				(5.8)			(5.8)
Repurchase of common stock	(51.2)						(51.2)	(51.2)
Common stock dividends	(49.3)				(49.3)			(49.3)
Stock-based compensation, shares		2.2
Stock-based compensation, value	32.0		0.2	31.8				32.0
Exercise of stock options, shares		0.9
Exercise of stock options, value	9.2		0.1	9.1				9.2
Shares withheld for taxes, shares		(0.8)
Shares withheld for taxes, value	(17.1)		(0.1)	(17.0)				(17.1)
Excess tax benefit from stock-based compensation	8.5			8.5				8.5
Other	(0.1)			0.1	(0.2)			(0.1)
Balance at Mar. 31, 2015	$ 1,944.7		$ 41.4	$ 1,580.0	$ 1,126.2	$ (764.7)	$ (70.2)	$ 1,912.7	$ 32.0
Balance, Common Stock Shares at Mar. 31, 2015		416.9