CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 127.1	$ 24.2	$ 205.4	$ 357.4
Foreign currency translation:
Foreign currency translation adjustments	(12.2)	76.5	190.0	(4.8)
Reclassification adjustments recognized in net income	0.0	1.2	20.3	1.2
Foreign currency transaction and translation adjustment, net of tax	(12.2)	77.7	210.3	(3.6)
Derivative instruments:
Recognition of previously unrealized net gain in net income	(0.9)	(1.0)	(2.9)	(2.8)
Income tax effect	0.2	0.3	0.7	0.7
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	(0.7)	(0.7)	(2.2)	(2.1)
Defined benefit pension and other postretirement plans:
Net actuarial gain for the period	0.5	0.0	0.1	0.3
Amortization of unrecognized losses, transition obligation and prior service cost included in net income	2.3	1.9	6.8	5.6
Settlement gains (losses) included in net income	8.5	(0.1)	8.5	(0.2)
Other	0.0	0.1	(0.1)	0.4
Income tax effect	(2.9)	(0.5)	(3.9)	(1.3)
Defined benefit pension and other postretirement plans adjustment, net of tax	8.4	1.4	11.4	4.8
Other comprehensive (loss) income, net of tax	(4.5)	78.4	219.5	(0.9)
TOTAL COMPREHENSIVE INCOME	122.6	102.6	424.9	356.5
Less: comprehensive income attributable to non-controlling interests	2.8	4.6	4.9	11.4
COMPREHENSIVE INCOME ATTRIBUTABLE TO IPG	$ 119.8	$ 98.0	$ 420.0	$ 345.1