Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
NET INCOME		$ 123.8	$ 103.7	$ 119.6	$ 81.3
Foreign Currency Translation
Foreign currency translation adjustments		26.1	25.5	(109.0)	24.5
Less: reclassification adjustments recognized in net income		(0.7)	0.0	(1.2)	(0.9)
Foreign Currency Translation Net of Tax		25.4	25.5	(110.2)	23.6
Available-for-sale Securities
Changes in fair value of available-for-sale securities		0.0	0.1	0.2	0.2
Income tax effect		(0.2)	0.0	0.1	0.0
Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax		0.2	0.1	0.1	0.2
Derivative Instruments
Changes in fair value of derivative instruments		0.0	0.0	0.0	(0.6)
Less: recognition of previously unrealized losses included in net income		(0.5)	(0.5)	(1.0)	(0.9)
Income tax effect		0.2	0.2	0.4	0.1
Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		0.3	0.3	0.6	0.2
Defined Benefit Pension and Other Postretirement Plans
Net actuarial gains (losses) for the period		1.3	0.0	5.7	(0.3)
Less: amortization of unrecognized losses, transition obligation and prior service cost included in net income	[1]	3.2	2.4	6.2	5.0
Less: settlement and curtailment losses included in net income		0.2	0.0	0.2	0.0
Other		(0.3)	(0.1)	(0.2)	(0.2)
Income tax effect		(1.3)	(0.7)	(2.2)	(1.3)
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		(3.1)	(1.6)	(9.7)	(3.2)
Other comprehensive income (loss), net of tax		29.0	27.5	(99.8)	27.2
TOTAL COMPREHENSIVE INCOME		152.8	131.2	19.8	108.5
Less: comprehensive income (loss) attributable to noncontrolling interests		2.7	4.0	(0.5)	1.9
COMPREHENSIVE INCOME ATTRIBUTABLE TO IPG		$ 150.1	$ 127.2	$ 20.3	$ 106.6

[1] These accumulated other comprehensive loss components are included in the computation of net periodic cost. See Note 9 for further information.