Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
NET (LOSS) INCOME	$ (16.1)	$ 21.3
Foreign currency translation:
Foreign currency translation adjustments	22.4	52.9
Reclassification adjustments recognized in net income	12.5	(0.4)
Foreign currency transaction and translation adjustment, net of tax	34.9	52.5
Available-for-sale securities:
Changes in fair value of available-for sale securities	0.0	0.1
Net unrealized gains/losses on available-for-sale securities, net of tax	0.0	0.1
Derivative instruments:
Recognition of previously unrealized losses in net income	0.5	0.5
Income tax effect	(0.2)	(0.2)
Net unrecognized gains/losses on derivative instruments, net of tax	0.3	0.3
Defined benefit pension and other postretirement plans:
Amortization of unrecognized losses, transition obligation and prior service cost included in net income	1.9	1.7
Settlement and curtailment losses included in net income	0.2	0.0
Other	0.1	(0.2)
Income tax effect	(0.1)	(0.1)
Defined benefit pension and other postretirement plans adjustment, net of tax	2.1	1.4
Other comprehensive income, net of tax	37.3	54.3
TOTAL COMPREHENSIVE INCOME	21.2	75.6
Less: comprehensive loss attributable to noncontrolling interests	(1.7)	(2.9)
COMPREHENSIVE INCOME ATTRIBUTABLE TO IPG	$ 22.9	$ 78.5