Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 24.2	$ 245.7	$ 357.4	$ 646.5
Foreign currency translation:
Foreign currency translation adjustments	76.5	(60.6)	(4.8)	(29.1)
Reclassification adjustments recognized in net income	1.2	(0.0)	1.2	0.5
Foreign currency transaction and translation adjustment, net of tax	77.7	(60.6)	(3.6)	(28.6)
Derivative Instrument:
Changes in fair value of derivative instruments	0.0	0.0	0.0	0.6
Recognition of previously unrealized gain in net income	(1.0)	(1.1)	(2.8)	(1.7)
Income tax effect	0.3	0.3	0.7	0.3
Net unrecognized gains on derivative instruments, net of tax	(0.7)	(0.8)	(2.1)	(0.8)
Defined benefit pension and other postretirement plans:
Net actuarial gains for the period	0.0	0.0	0.3	2.7
Amortization of unrecognized losses, transition obligation and prior service cost included in net income	1.9	1.8	5.6	5.2
Settlement losses included in net income	(0.1)	0.0	(0.2)	0.0
Other	0.1	(0.1)	0.4	0.3
Income tax effect	(0.5)	(0.4)	(1.3)	(1.4)
Defined benefit pension and other postretirement plans adjustment, net of tax	1.4	1.3	4.8	6.8
Other comprehensive loss, net of tax	78.4	(60.1)	(0.9)	(22.6)
TOTAL COMPREHENSIVE INCOME	102.6	185.6	356.5	623.9
Less: comprehensive income attributable to noncontrolling interests	4.6	1.7	11.4	10.8
COMPREHENSIVE INCOME ATTRIBUTABLE TO IPG	$ 98.0	$ 183.9	$ 345.1	$ 613.1