Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 2.6	$ (9.5)
Foreign currency translation:
Foreign currency translation adjustments	(147.6)	8.3
Reclassification adjustments recognized in net income (loss)	(3.6)	1.2
Foreign currency transaction and translation adjustment, net of tax	(151.2)	9.5
Derivative Instrument:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(1.2)	0.0
Recognition of previously unrealized losses in net income (loss)	0.6	0.6
Income tax effect	(0.1)	(0.1)
Net unrecognized gains on derivative instruments, net of tax	0.1	0.5
Defined benefit pension and other postretirement plans:
Amortization of unrecognized losses, transition obligation and prior service cost included in net income (loss)	1.9	1.7
Other	(1.3)	(0.3)
Income tax effect	(0.3)	(0.1)
Defined benefit pension and other postretirement plans adjustment, net of tax	0.3	1.3
Other comprehensive loss, net of tax	(150.8)	11.3
TOTAL COMPREHENSIVE (LOSS) INCOME	(148.2)	1.8
Less: comprehensive income attributable to noncontrolling interests	(4.2)	(1.6)
COMPREHENSIVE (LOSS) INCOME ATTRIBUTABLE TO IPG	$ (144.0)	$ 3.4