Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 278.5	$ 168.4	$ 237.2	$ 331.7
Foreign currency translation:
Foreign currency translation adjustments	46.5	(50.9)	(58.3)	(38.4)
Reclassification adjustments recognized in net income	9.6	(0.6)	9.3	5.2
Foreign currency transaction and translation adjustment, net of tax	56.1	(51.5)	(49.0)	(33.2)
Derivative Instrument:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	4.5	0.0	3.6	0.0
Recognition of previously unrealized losses in net income	0.6	0.6	1.8	1.8
Income tax effect	(1.3)	(0.2)	(1.4)	(0.4)
Net unrecognized gains on derivative instruments, net of tax	3.8	0.4	4.0	1.4
Defined benefit pension and other postretirement plans:
Net actuarial gains for the period	0.0	0.0	2.2	0.7
Amortization of unrecognized losses, transition obligation and prior service cost included in net income	1.8	1.7	5.5	5.0
Other	0.4	(0.1)	(1.0)	0.2
Income tax effect	(0.4)	(0.2)	(1.6)	(0.4)
Defined benefit pension and other postretirement plans adjustment, net of tax	1.8	1.4	5.1	5.5
Other comprehensive income (loss), net of tax	61.7	(49.7)	(39.9)	(26.3)
TOTAL COMPREHENSIVE INCOME	340.2	118.7	197.3	305.4
Less: comprehensive (loss) income attributable to noncontrolling interests	(0.8)	1.4	(3.7)	3.4
COMPREHENSIVE INCOME ATTRIBUTABLE TO IPG	$ 341.0	$ 117.3	$ 201.0	$ 302.0