CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Assets, Current [Abstract]
Cash and cash equivalents	$ 114,935	$ 104,537
Accounts receivable, net	727,583	735,752
Expenditures billable to clients	170,293	164,694
Other current assets	202,210	157,309
Assets, Current, Total	1,215,021	1,162,292
Fixed assets, net	71,069	73,081
Operating Lease, Right-of-Use Asset	202,796	213,576
Goodwill	1,596,242	1,595,238
Other intangible assets, net	822,840	834,248
Deferred Tax Assets, Tax Deferred Expense	280,064	281,057
Other assets	55,005	55,055
Assets, Total	4,243,037	4,214,547
Liabilities, Current [Abstract]
Accounts payable	526,097	548,320
Accrued media	207,082	239,490
Accruals and other liabilities	266,081	291,554
Advance billings	392,959	329,815
Current portion of lease liabilities - operating leases	54,331	55,386
Current portion of deferred acquisition consideration	22,303	15,446
Liabilities, Current, Total	1,468,853	1,480,011
Long-term debt	1,439,736	1,326,013
Long-term portion of deferred acquisition consideration	27,755	24,598
Long-term lease liabilities - operating leases	213,807	224,397
Deferred Tax Liabilities, Tax Deferred Income	52,813	54,726
Long-term tax receivable agreement liability	252,390	252,390
Other liabilities	40,858	51,077
Liabilities, Total	3,496,212	3,413,212
Redeemable Noncontrolling Interest, Equity, Fair Value	24,317	24,968
Commitments and Contingencies
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Paid-in capital	711,490	744,463
Retained earnings	20,082	32,930
Accumulated other comprehensive loss	(26,910)	(19,252)
Stagwell Inc. shareholders’ equity	704,908	758,393
Noncontrolling interests	17,600	17,974
Total shareholders’ equity	722,508	776,367
Liabilities and Equity, Total	4,243,037	4,214,547
Common Class A and Common Class B
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common shares	$ 246	$ 252