Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 3,623.8	$ 3,714.3	$ 10,812.5	$ 11,203.5
Salary and service costs	2,704.7	2,834.2	7,937.5	8,319.9
Occupancy and other costs	290.7	376.8	915.4	1,016.7
Net gain on disposition of subsidiaries	0.0	(178.4)	0.0	(178.4)
Cost of services	2,995.4	3,032.6	8,852.9	9,158.2
Selling, general and administrative expenses	97.2	113.5	308.4	336.3
Depreciation and amortization	57.9	65.9	175.3	202.7
Operating Expenses	3,150.5	3,212.0	9,336.6	9,697.2
Operating Profit	473.3	502.3	1,475.9	1,506.3
Interest Expense	62.8	69.4	192.4	198.1
Interest Income	13.5	12.7	46.9	42.0
Income Before Income Taxes and Income From Equity Method Investments	424.0	445.6	1,330.4	1,350.2
Income Tax Expense	112.3	115.3	345.5	343.0
Income From Equity Method Investments	0.5	1.0	1.2	3.6
Net Income	312.2	331.3	986.1	1,010.8
Net Income Attributed To Noncontrolling Interests	22.0	32.4	62.0	83.6
Net Income - Omnicom Group Inc.	$ 290.2	$ 298.9	$ 924.1	$ 927.2
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 1.33	$ 1.33	$ 4.19	$ 4.08
Diluted	$ 1.32	$ 1.32	$ 4.17	$ 4.06