Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net revenue	$ 2,004.8	$ 1,774.0
Billable expenses	356.4	395.1
Total revenue	2,361.2	2,169.1
OPERATING EXPENSES:
Salaries and related expenses	1,421.1	1,330.3
Office and other direct expenses	389.2	323.8
Billable expenses	356.4	395.1
Cost of services	2,166.7	2,049.2
Selling, general and administrative expenses	41.4	35.1
Depreciation and amortization	71.1	46.0
Restructuring Charges	31.8	0.0
Total operating expenses	2,311.0	2,130.3
OPERATING INCOME	50.2	38.8
EXPENSES AND OTHER INCOME:
Interest expense	(49.8)	(19.9)
Interest income	7.8	4.0
Other expense, net	(6.9)	(24.4)
Total (expenses) and other income	(48.9)	(40.3)
Income (loss) before income taxes	1.3	(1.5)
Provision for income taxes	10.5	12.7
Loss of consolidated companies	(9.2)	(14.2)
Equity in net loss of unconsolidated affiliates	(0.3)	(1.9)
NET LOSS	(9.5)	(16.1)
Net loss attributable to noncontrolling interests	1.5	2.0
NET LOSS AVAILABLE TO IPG COMMON STOCKHOLDERS	$ (8.0)	$ (14.1)
Loss per share, Basic	$ (0.02)	$ (0.04)
Loss per share, Diluted	$ (0.02)	$ (0.04)
Weighted-average number of common shares outstanding, Basic	384.5	383.4
Weighted-average number of common shares outstanding, Diluted	384.5	383.4