Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 3,719.8	$ 3,859.6	$ 7,188.7	$ 7,489.2
Salary and service costs	2,665.2	2,772.9	5,232.8	5,485.7
Occupancy and other costs	315.4	319.6	624.7	639.9
Cost of services	2,980.6	3,092.5	5,857.5	6,125.6
Selling, general and administrative expenses	107.7	117.4	211.2	222.9
Depreciation and amortization	57.8	67.4	117.4	136.8
Operating Expenses	3,146.1	3,277.3	6,186.1	6,485.3
Operating Profit	573.7	582.3	1,002.6	1,003.9
Interest Expense	66.6	66.4	129.6	128.6
Interest Income	16.4	13.9	33.4	29.3
Income Before Income Taxes and Income From Equity Method Investments	523.5	529.8	906.4	904.6
Income Tax Expense	130.6	136.7	233.2	227.7
Income From Equity Method Investments	1.2	1.7	0.7	2.6
Net Income	394.1	394.8	673.9	679.5
Net Income Attributed To Noncontrolling Interests	23.4	30.6	40.0	51.2
Net Income - Omnicom Group Inc.	$ 370.7	$ 364.2	$ 633.9	$ 628.3
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 1.69	$ 1.61	$ 2.86	$ 2.75
Diluted	1.68	1.60	2.85	2.73
Dividends Declared Per Common Share	$ 0.65	$ 0.60	$ 1.30	$ 1.20