Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income available to IPG common stockholders	$ (45.6)	$ 169.5	$ (40.9)	$ 161.5
Weighted-average number of common shares outstanding, Basic	389.4	386.2	388.5	385.4
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements		5.0		4.7
Weighted-average number of common shares outstanding, Diluted	389.4	391.2	388.5	390.1
Loss per share, Basic	$ (0.12)	$ 0.44	$ (0.11)	$ 0.42
Loss per share, Diluted	$ (0.12)	$ 0.43	$ (0.11)	$ 0.41
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2.9		3.3