Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 673.9	$ 637.7	$ 570.4
Foreign Currency Translation:
Foreign currency translation adjustments	11.3	(149.6)	133.7
Reclassification adjustments recognized in net income	6.7	15.7	1.1
Foreign currency translation, net of tax	18.0	(133.9)	134.8
Available-for-sale securities:
Changes in fair value of available-for-sale securities	0.0	0.0	0.0
Recognition of previously unrealized gains in net income	(0.0)	(0.0)	(0.7)
Income tax effect	(0.0)	(0.0)	0.1
Available-for-sale securities, net of tax	0.0	0.0	(0.6)
Derivatives instruments:
Recognition of previously unrealized losses included in net income	2.3	2.2	2.1
Income tax effect	(0.5)	(0.7)	(0.5)
Derivative instruments, net of tax	1.8	1.5	1.6
Defined benefit pension and other postretirement plans:
Net actuarial (losses) gains for the period	(14.8)	12.6	(13.6)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	6.7	7.5	6.9
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	0.0	(1.0)	6.8
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Other, before Tax	(2.5)	(1.0)	2.7
Income tax effect	1.2	(1.8)	(0.5)
Defined benefit pension and other postretirement plans, net of tax	(9.4)	16.3	2.3
Other comprehensive income (loss), net of tax	10.4	(116.1)	138.1
Total comprehensive income	684.3	521.6	708.5
Less: comprehensive income attributable to noncontrolling interests	17.2	16.0	17.5
Comprehensive Income Attributable to IPG	$ 667.1	$ 505.6	$ 691.0