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
Common Stock, shares		387.0
Changes related to lease standard update	$ (6.6)				$ (6.6)		$ (6.6)
Balance at Dec. 31, 2019	2,825.6		$ 38.7	$ 977.3	2,689.9	$ (930.0)	2,775.9	$ 49.7
Net income	2.6
Net income available to IPG common stockholders	4.7				4.7		4.7
Net income attributable to noncontrolling interest	(2.1)							(2.1)
Other comprehensive income (loss)	(150.8)					(148.7)	(148.7)
Other comprehensive loss, attributable to noncontrolling interest								(2.1)
Reclassifications related to redeemable noncontrolling interests	(2.8)							(2.8)
Distributions to noncontrolling interests	(5.6)							5.6
Change in redemption value of redeemable noncontrolling interests	3.1				3.1		3.1
Common stock dividends	(100.0)				(100.0)		(100.0)
Stock-based compensation, shares		3.4
Stock-based compensation, value	25.4		0.3	25.1			25.4
Exercise of stock options, shares		0.0
Exercise of stock options, value	0.2		0.0	0.2			0.2
Shares withheld for taxes, shares		(0.9)
Shares withheld for taxes, value	(21.5)		0.1	21.4			21.5
Balance at Mar. 31, 2020	2,575.2		38.9	981.2	2,591.1	(1,078.7)	2,532.5	42.7
Common Stock, shares		389.5
Common Stock, shares		390.9
Balance at Dec. 31, 2020	2,943.9		39.0	1,099.3	2,636.9	(880.2)	2,895.0	48.9
Net income	92.4
Net income available to IPG common stockholders	91.7				91.7		91.7
Net income attributable to noncontrolling interest	0.7							0.7
Other comprehensive income (loss)	(16.2)					(16.1)	(16.1)
Other comprehensive loss, attributable to noncontrolling interest								(0.1)
Reclassifications related to redeemable noncontrolling interests	(1.0)							(1.0)
Distributions to noncontrolling interests	(3.3)							3.3
Change in redemption value of redeemable noncontrolling interests	1.0				1.0		1.0
Common stock dividends	(106.5)				(106.5)		(106.5)
Stock-based compensation, shares		2.6
Stock-based compensation, value	23.7		0.3	23.4			23.7
Exercise of stock options, shares		0.6
Exercise of stock options, value	8.3		0.1	8.2			8.3
Shares withheld for taxes, shares		(0.9)
Shares withheld for taxes, value	(23.1)		0.1	23.0			23.1
Other	(0.4)							(0.4)
Balance at Mar. 31, 2021	$ 2,921.6		$ 39.3	$ 1,107.9	$ 2,623.1	$ (896.3)	$ 2,874.0	$ 47.6
Common Stock, shares		393.2