Significant Accounting Policies Basis of Presentation (Policies)	12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Basis of Presentation We conduct our business across three reportable segments described in Note 16. The three reportable segments are: Media, Data & Engagement Solutions ("MD&E"), Integrated Advertising & Creativity Led Solutions ("IA&C"), and Specialized Communications & Experiential Solutions ("SC&E"). Cost of services is comprised of the expenses of our revenue-producing operating segments including salaries and related expenses, office and other direct expenses and billable expenses, as well as an allocation of the centrally managed expenses from Corporate and other. Office and other direct expenses include rent expense, professional fees, certain expenses incurred by our staff in servicing our clients and other costs directly attributable to client engagements. Selling, general and administrative expenses are primarily the unallocated expenses from Corporate and other excluding depreciation and amortization. Depreciation and amortization of the fixed assets and intangible assets of the Company is disclosed as a separate operating expense. Impairment of goodwill is disclosed as a separate operating expense. Restructuring charges in 2024 consist of adjustments to the Company's restructuring actions taken in 2022 and 2020, and primarily relate to real estate actions which were designed to reduce our real estate footprint and to better align our cost structure with revenue.
Lessee, Leases [Policy Text Block]	Leases As of December 31, 2024, we do not have a material amount of finance leases and the majority of our operating leases, for which we serve as the lessee, consist primarily of real-estate property for our offices around the world. Both the right-of-use asset and lease liability are measured at the present value of the future lease payments, with the asset being subject to adjustments such as initial direct costs, prepaid lease payments, and lease incentives. Many of our leases provide for renewal and/or termination options, as well as escalation clauses, which are also factored into our lease payments when appropriate. The discount rate used to measure the lease asset and liability is determined at the beginning of the lease term using the rate implicit in the lease, if readily determinable, or using the Company's collateralized credit-adjusted borrowing rate.
Property and Equipment	Property and Equipment Furniture, equipment, leasehold improvements and buildings are stated at cost, net of accumulated depreciation. Furniture and equipment are depreciated generally using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years for furniture and equipment, 10 to 35 years for buildings and the shorter of the useful life or the remaining lease term for leasehold improvements. Land is stated at cost and is not depreciated. We capitalize certain internal and external costs incurred to acquire or create internal use software, principally related to our enterprise resource planning (“ERP”) systems. Our ERP systems are stated at cost, net of accumulated amortization, and are amortized using the straight-line method over 10 years. All other internal use computer software are stated at cost, net of accumulated amortization and are amortized using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years.

Significant Accounting Policies Basis of Presentation (Policies)

12 Months Ended

Dec. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]

Basis of Presentation

We conduct our business across three reportable segments described in Note 16. The three reportable segments are: Media, Data & Engagement Solutions ("MD&E"), Integrated Advertising & Creativity Led Solutions ("IA&C"), and Specialized Communications & Experiential Solutions ("SC&E").

Cost of services is comprised of the expenses of our revenue-producing operating segments including salaries and related expenses, office and other direct expenses and billable expenses, as well as an allocation of the centrally managed expenses from Corporate and other. Office and other direct expenses include rent expense, professional fees, certain expenses incurred by our staff in servicing our clients and other costs directly attributable to client engagements.

Selling, general and administrative expenses are primarily the unallocated expenses from Corporate and other excluding depreciation and amortization.

Depreciation and amortization of the fixed assets and intangible assets of the Company is disclosed as a separate operating expense.

Impairment of goodwill is disclosed as a separate operating expense.

Restructuring charges in 2024 consist of adjustments to the Company's restructuring actions taken in 2022 and 2020, and primarily relate to real estate actions which were designed to reduce our real estate footprint and to better align our cost structure with revenue.

Lessee, Leases [Policy Text Block]

Leases

As of December 31, 2024, we do not have a material amount of finance leases and the majority of our operating leases, for which we serve as the lessee, consist primarily of real-estate property for our offices around the world. Both the right-of-use asset and lease liability are measured at the present value of the future lease payments, with the asset being subject to adjustments such as initial direct costs, prepaid lease payments, and lease incentives. Many of our leases provide for renewal and/or termination options, as well as escalation clauses, which are also factored into our lease payments when appropriate. The discount rate used to measure the lease asset and liability is determined at the beginning of the lease term using the rate implicit in the lease, if readily determinable, or using the Company's collateralized credit-adjusted borrowing rate.

Property and Equipment

Furniture, equipment, leasehold improvements and buildings are stated at cost, net of accumulated depreciation. Furniture and equipment are depreciated generally using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years for furniture and equipment, 10 to 35 years for buildings and the shorter of the useful life or the remaining lease term for leasehold improvements. Land is stated at cost and is not depreciated.

We capitalize certain internal and external costs incurred to acquire or create internal use software, principally related to our enterprise resource planning (“ERP”) systems. Our ERP systems are stated at cost, net of accumulated amortization, and are amortized using the straight-line method over 10 years. All other internal use computer software are stated at cost, net of accumulated amortization and are amortized using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years.