Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock, Shares	Common Stock, Amount	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss, Net of Tax	Total IPG Stockholders' Equity	Noncontrolling Interests	Treasury Stock, Common
Common Stock, shares		383.0
Balance at Dec. 31, 2023	$ 4,003.8		$ 38.3	$ 728.5	$ 4,254.5	$ (946.2)	$ 3,942.6	$ 61.2	$ (132.5)
NET INCOME (LOSS)	113.6
Net income available to IPG common stockholders	110.4				110.4		110.4
Net income attributable to noncontrolling interest	3.2							3.2
Other comprehensive loss	(50.7)					(49.5)	(49.5)
Other comprehensive loss, attributable to noncontrolling interest								(1.2)
Reclassifications related to redeemable noncontrolling interests	(0.3)							(0.3)
Distributions to noncontrolling interests	(4.3)							4.3
Change in redemption value of redeemable noncontrolling interests	0.0				0.0		0.0
Repurchases of common stock including excise tax	(62.9)
Payments for Repurchase of Common Stock	(62.4)						62.9		62.9
Common stock dividends	(125.8)				(125.8)		(125.8)
Stock-based compensation, shares		0.9
Stock-based compensation, value	22.8			22.8			22.8
Shares withheld for taxes, shares		(0.4)
Shares withheld for taxes, value	(13.3)			13.3			13.3
Other	0.4			0.2			(0.2)	0.2
Balance at Mar. 31, 2024	3,883.1		38.3	737.8	4,239.1	(995.7)	3,824.1	59.0	(195.4)
Common Stock, shares		383.5
Common Stock, shares		372.4
Balance at Dec. 31, 2024	3,864.5		37.2	432.6	4,440.2	(1,112.6)	3,797.4	67.1	0.0
NET INCOME (LOSS)	(85.3)
Net income available to IPG common stockholders	(85.4)				(85.4)		(85.4)
Net income attributable to noncontrolling interest	0.1							0.1
Other comprehensive loss	85.7					85.5	85.5
Other comprehensive loss, attributable to noncontrolling interest								0.2
Reclassifications related to redeemable noncontrolling interests	(0.6)							(0.6)
Distributions to noncontrolling interests	(7.4)							7.4
Change in redemption value of redeemable noncontrolling interests	0.0				0.0		0.0
Repurchase of common stock including excise tax	(90.6)
Payments for Repurchase of Common Stock	(90.0)						90.6		90.6
Common stock dividends	(124.1)				(124.1)		(124.1)
APIC, Share-Based Payment Arrangement, Option, Increase for Cost Recognition			0.2
Stock-based compensation, shares		1.8
Stock-based compensation, value	17.4			17.2			17.4
Shares withheld for taxes, shares		(0.6)
Shares withheld for taxes, value	(16.0)		0.1	15.9			16.0
Other	0.1			0.1			(0.1)	(0.2)
Balance at Mar. 31, 2025	$ 3,644.9		$ 37.3	$ 433.8	$ 4,230.7	$ (1,027.1)	$ 3,584.1	$ 60.8	$ (90.6)
Common Stock, shares		373.6