| Income Statement [Abstract] | |
| REVENUE | 3.4B |
| OPERATING EXPENSES | 3.03B |
| OPERATING INCOME | 371.7M |
| INTEREST EXPENSE | 49M |
| INTEREST INCOME | 8.1M |
| INCOME BEFORE INCOME TAXES AND INCOME FROM EQUITY METHOD INVESTMENTS | 330.8M |
| INCOME TAX EXPENSE | 109.2M |
| INCOME FROM EQUITY METHOD INVESTMENTS | 3.2M |
| NET INCOME | 224.8M |
| LESS: NET INCOME ATTRIBUTED TO NONCONTROLLING INTERESTS | 19.7M |
| NET INCOME - OMNICOM GROUP INC. | 205.1M |
| NET INCOME PER COMMON SHARE - OMNICOM GROUP INC.: | |
| Basic | 0.76 |
| Diluted | 0.76 |
| DIVIDENDS DECLARED PER COMMON SHARE | 0.4 |