Accumulated Other Comprehensive Loss, Net of Tax - Reclassification from Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net	$ (1.4)	$ (1.2)	$ (38.3)	$ (10.7)
Other expense, net, Interest expense	(25.7)	(22.5)	(78.1)	(46.1)
Provision for income taxes	(54.6)	(75.6)	(45.4)	(122.9)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	162.5	214.5	77.1	324.9
Reclassification Out of Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes	0.3	0.2	0.6	0.5
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	1.0	0.6	22.2	1.3
Derivative Instruments | Reclassification Out of Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net	0.0	0.0	20.3	0.0
Other expense, net, Interest expense	(1.0)	(0.9)	(2.0)	(1.8)
Defined Benefit Pension and Other Postretirement Plans | Reclassification Out of Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other expense, net	$ 2.3	$ 1.7	$ 4.5	$ 3.6