Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Net income available to IPG common stockholders	$ 243.7	$ 251.8	$ 635.2	$ 640.8
Weighted-average number of common shares outstanding, Basic	383.6	390.6	385.0	392.7
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1.9	3.5	1.8	3.5
Weighted-average number of common shares outstanding, Diluted	385.5	394.1	386.8	396.2
Earnings per share, Basic	$ 0.64	$ 0.64	$ 1.65	$ 1.63
Earnings per share, Diluted	$ 0.63	$ 0.64	$ 1.64	$ 1.62