Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Net income available to IPG common stockholders	$ 20.1	$ 243.7	$ 345.0	$ 635.2
Weighted-average number of common shares outstanding, Basic	373.9	383.6	376.2	385.0
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	2.9	1.9	2.5	1.8
Weighted-average number of common shares outstanding, Diluted	376.8	385.5	378.7	386.8
Earnings per share, Basic	$ 0.05	$ 0.64	$ 0.92	$ 1.65
Earnings per share, Diluted	$ 0.05	$ 0.63	$ 0.91	$ 1.64