Acquisitions and Dispositions - Narrative (Details) $ / shares in Units, £ in Thousands, shares in Thousands	Oct. 03, 2022 USD ($)	Jul. 15, 2022 USD ($)	Jul. 12, 2022 USD ($)	May 31, 2022 USD ($)	Apr. 19, 2022 USD ($)	Apr. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 01, 2021 USD ($)	Oct. 01, 2021 USD ($)	Aug. 02, 2021 USD ($) $ / shares shares	Jul. 31, 2023	Sep. 30, 2022 USD ($)	Dec. 31, 2021 GBP (£)
Business Acquisition [Line Items]
Goodwill							$ 1,652,723,000						$ 1,615,694,000
Payments for Acquire Businesses, Working Capital Payments | £								£ 9
Stagwell Media
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash											$ 1.80
MDC
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable											$ 80,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life											13 years
Goodwill											$ 1,290,347,000
Business Acquisition, Share Price | $ / shares											$ 5.42
MDC | Previously Reported Goodwill
Business Acquisition [Line Items]
Goodwill											$ 1,298,370,000
MDC | Common Class C | Stagwell Media
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions | shares											179,970
MDC | Common Units | Stagwell OpCo
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)											69.55%
MDC | Integrated Agencies Network
Business Acquisition [Line Items]
Goodwill											$ 932,582,000
MDC | Media Network
Business Acquisition [Line Items]
Goodwill											285,396,000
MDC | Communications Network
Business Acquisition [Line Items]
Goodwill											72,369,000
Goodstuff Holdings Limited
Business Acquisition [Line Items]
Closing cash payment | £								21
Goodwill							$ 4,410,000
Payment for contingent consideration | £								8
Payments to Acquire Businesses, Deferred Payments | £								4
Payment for contingent consideration | £								8
Payments to Acquire Businesses, Deferred Payments | £								£ 4
Goodstuff Holdings Limited | Maximum
Business Acquisition [Line Items]
Deferred acquisition consideration | £														£ 22
Targeted Victory
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)										27.00%
Aggregate purchase price										$ 73,898,000
Deferred acquisition consideration										$ 46,618,000
Business Acquisition, Percentage of Voting Interests Acquired, Step One										13.30%
Business Combination, Consideration Transferred, Redeemable Noncontrolling Interest										$ 27,280,000
Business Acquisition, Percentage of Voting Interests Acquired, Step One										13.30%
Business Combination, Consideration Transferred, Redeemable Noncontrolling Interest										$ 27,280,000
Targeted Victory | Forecast
Business Acquisition [Line Items]
Business Acquisitions, Percentage of Voting Interests Acquired, Step Two												13.30%
Business Acquisitions, Percentage of Voting Interests Acquired, Step Two												13.30%
Targeted Victory | Common Class A
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Purchase Price Option Sacrificed in Shares, Percentage										50.00%
Business Combination, Contingent Consideration Arrangements, Change in Range of Outcomes, Contingent Consideration, Liability, Value, High										$ 135,000
Business Combination, Contingent Consideration Arrangements, Purchase Price Option Sacrificed in Shares, Percentage										50.00%
Business Combination, Contingent Consideration Arrangements, Change in Range of Outcomes, Contingent Consideration, Liability, Value, High										$ 135,000
Concentric
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)									27.00%
Aggregate purchase price									$ 8,058,000
Closing cash payment									1,581,000
Deferred acquisition consideration									$ 6,477,000
Instrument Holdings Inc.
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)							49.00%							49.00%
Aggregate purchase price							$ 157,072,000
Closing cash payment							37,500,000
Business Combination, Consideration Transferred, Deferred Acquisition Payment							82,072,000
Business Combination, Consideration Transferred, Deferred Acquisition Payment							82,072,000
Instrument Holdings Inc. | Common Class A
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable							$ 37,500,000
Hello Design
Business Acquisition [Line Items]
Aggregate purchase price						$ 4,600,000
Closing cash payment						3,600,000
Deferred acquisition consideration						$ 1,000,000
BNG
Business Acquisition [Line Items]
Aggregate purchase price					$ 20,695,000
Goodwill											$ 25,552,000
Estimated contingent consideration					$ 50,000,000
Contingent consideration payable in cash (percent)					67.00%
Contingent consideration payable in equity (percent)					33.00%
TMA Direct
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)				87.00%
Aggregate purchase price				$ 17,247,000
Deferred acquisition consideration				457,000
Goodwill				$ 6,569,000
Business Acquisition, Percentage of Voting Interests Acquired, Step One				13.00%
Business Combination, Contingent Consideration Arrangements, Change in Range of Outcomes, Contingent Consideration, Liability, Value, High				$ 13,330,000
Business Acquisition, Percentage of Voting Interests Acquired, Step One				13.00%
Business Combination, Contingent Consideration Arrangements, Change in Range of Outcomes, Contingent Consideration, Liability, Value, High				$ 13,330,000
Epicenter | Subsequent event
Business Acquisition [Line Items]
Aggregate purchase price	$ 9,729,000
Estimated contingent consideration	$ 5,000,000
PEP Group
Business Acquisition [Line Items]
Aggregate purchase price			$ 521,000
Estimated contingent consideration			$ 2,679,000
Apollo
Business Acquisition [Line Items]
Aggregate purchase price		$ 2,300,000
Payments to Acquire Business, First Payment		1,000
Payments to Acquire Business, Second Payment		$ 1,500,000