Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 92.4	$ 2.6
Foreign currency translation:
Foreign currency translation adjustments	(41.0)	(147.6)
Reclassification adjustments recognized in net income	0.7	(3.6)
Foreign currency transaction and translation adjustment, net of tax	(40.3)	(151.2)
Derivative Instrument:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	21.3	(0.4)
Recognition of previously unrealized losses in net income	5.2	0.6
Income tax effect	(4.2)	(0.1)
Net unrecognized gains on derivative instruments, net of tax	22.3	0.1
Defined benefit pension and other postretirement plans:
Amortization of unrecognized losses, transition obligation and prior service cost included in net income	2.3	1.9
Other	(0.1)	(1.3)
Income tax effect	(0.4)	(0.3)
Defined benefit pension and other postretirement plans adjustment, net of tax	1.8	0.3
Other comprehensive income (loss), net of tax	(16.2)	(150.8)
TOTAL COMPREHENSIVE INCOME	76.2	(148.2)
Less: comprehensive (loss) income attributable to noncontrolling interests	0.6	(4.2)
COMPREHENSIVE INCOME ATTRIBUTABLE TO IPG	$ 75.6	$ (144.0)