Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income available to IPG common stockholders	$ 91.7	$ 4.7
Weighted-average number of common shares outstanding, Basic	391.5	387.7
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	4.5	4.0
Weighted-average number of common shares outstanding, Diluted	396.0	391.7
Earnings per share, Basic	$ 0.23	$ 0.01
Earnings per share, Diluted	$ 0.23	$ 0.01