Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net loss available to IPG common stockholders	$ (8.0)	$ (14.1)
Weighted-average number of common shares outstanding, Basic	384.5	383.4
Dilutive effect of stock options and restricted shares	4.4	5.2
Weighted-average number of common shares outstanding, Diluted	384.5	383.4
Loss per share, Basic	$ (0.02)	$ (0.04)
Loss per share, Diluted	$ (0.02)	$ (0.04)