CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Millions, $ in Millions	Total	Total IPG Stockholders’ Equity	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated  Other Comprehensive Loss, Net of Tax	Treasury Stock	Non-controlling Interests
Beginning balance (in shares) at Dec. 31, 2023			383.0
Beginning balance at Dec. 31, 2023	$ 4,003.8	$ 3,942.6	$ 38.3	$ 728.5	$ 4,254.5	$ (946.2)	$ (132.5)	$ 61.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	357.4	345.0			345.0			12.4
Other comprehensive income (loss)	(0.9)	0.1				0.1		(1.0)
Reclassifications related to redeemable non-controlling interests	(4.0)	(2.7)		(2.7)				(1.3)
Distributions to non-controlling interests	(13.7)							(13.7)
Change in redemption value of redeemable non-controlling interests	(5.1)	(5.1)			(5.1)
Repurchase of common stock	(232.0)	(232.0)					(232.0)
Common stock dividends	(374.8)	(374.8)			(374.8)
Stock-based compensation (in shares)			1.3
Stock-based compensation			$ 0.1
Stock-based compensation	71.1	71.1		71.0
Shares withheld for taxes (in shares)			(0.4)
Shares withheld for taxes	(13.6)	(13.6)	$ (0.0)	(13.6)
Other	(3.5)	(4.8)		(4.8)				1.3
Ending balance (in shares) at Sep. 30, 2024			383.9
Ending balance at Sep. 30, 2024	3,784.7	3,725.8	$ 38.4	778.4	4,219.6	(946.1)	(364.5)	58.9
Beginning balance (in shares) at Jun. 30, 2024			383.7
Beginning balance at Jun. 30, 2024	3,895.0	3,835.6	$ 38.3	759.8	4,325.1	(1,024.0)	(263.6)	59.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24.2	20.1			20.1			4.1
Other comprehensive income (loss)	78.4	77.9				77.9		0.5
Reclassifications related to redeemable non-controlling interests	(0.9)	0.0		0.0				(0.9)
Distributions to non-controlling interests	(5.1)							(5.1)
Change in redemption value of redeemable non-controlling interests	(1.5)	(1.5)			(1.5)
Repurchase of common stock	(100.9)	(100.9)					(100.9)
Common stock dividends	(124.1)	(124.1)			(124.1)
Stock-based compensation (in shares)			0.2
Stock-based compensation			$ 0.1
Stock-based compensation	23.3	23.3		23.2
Shares withheld for taxes (in shares)			(0.0)
Shares withheld for taxes	(0.1)	(0.1)	$ (0.0)	(0.1)
Other	(3.6)	(4.5)		(4.5)				0.9
Ending balance (in shares) at Sep. 30, 2024			383.9
Ending balance at Sep. 30, 2024	3,784.7	3,725.8	$ 38.4	778.4	4,219.6	(946.1)	(364.5)	58.9
Beginning balance (in shares) at Dec. 31, 2024			372.4
Beginning balance at Dec. 31, 2024	3,864.5	3,797.4	$ 37.2	432.6	4,440.2	(1,112.6)	0.0	67.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	205.4	201.3			201.3			4.1
Other comprehensive income (loss)	219.5	218.7				218.7		0.8
Reclassifications related to redeemable non-controlling interests	1.9							1.9
Distributions to non-controlling interests	(28.0)							(28.0)
Change in redemption value of redeemable non-controlling interests	20.2	20.2			20.2
Repurchase of common stock	(259.5)	(259.5)					(259.5)
Common stock dividends	(367.0)	(367.0)			(367.0)
Stock-based compensation (in shares)			2.2
Stock-based compensation			$ 0.2
Stock-based compensation	62.2	62.2		62.0
Shares withheld for taxes (in shares)			(0.6)
Shares withheld for taxes	(16.2)	(16.2)	$ 0.0	(16.2)
Other	(8.0)	(0.3)		(0.3)				(7.7)
Ending balance (in shares) at Sep. 30, 2025			374.0
Ending balance at Sep. 30, 2025	3,695.0	3,656.8	$ 37.4	478.1	4,294.7	(893.9)	(259.5)	38.2
Beginning balance (in shares) at Jun. 30, 2025			373.8
Beginning balance at Jun. 30, 2025	3,765.0	3,712.4	$ 37.4	460.0	4,294.3	(889.5)	(189.8)	52.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	127.1	124.2			124.2			2.9
Other comprehensive income (loss)	(4.5)	(4.4)				(4.4)		(0.1)
Reclassifications related to redeemable non-controlling interests	(0.2)							(0.2)
Distributions to non-controlling interests	(9.6)							(9.6)
Change in redemption value of redeemable non-controlling interests	(2.8)	(2.8)			(2.8)
Repurchase of common stock	(69.7)	(69.7)					(69.7)
Common stock dividends	(121.0)	(121.0)			(121.0)
Stock-based compensation (in shares)			0.2
Stock-based compensation			$ 0.0
Stock-based compensation	18.3	18.3		18.3
Shares withheld for taxes (in shares)			(0.0)
Shares withheld for taxes	(0.2)	(0.2)	$ 0.0	(0.2)
Other	(7.4)	0.0		0.0				(7.4)
Ending balance (in shares) at Sep. 30, 2025			374.0
Ending balance at Sep. 30, 2025	$ 3,695.0	$ 3,656.8	$ 37.4	$ 478.1	$ 4,294.7	$ (893.9)	$ (259.5)	$ 38.2