UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	$ (9,959)	$ (4,667)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Stock-based compensation	31,497	21,991
Depreciation and amortization	83,375	76,837
Operating Lease, Right-of-Use Asset, Amortization Expense	34,075	39,534
Gain (Loss) on Termination of Lease	(3,529)
Impairment and other losses	0	1,715
Deferred income taxes	(1,424)	3,797
Adjustment To Deferred Acquisition Consideration	3,437	7,390
Other, net	(7,517)	3,850
Changes in working capital:
Accounts receivable	7,941	(30,157)
Expenditures billable to clients	27,021	(6,516)
Other assets	(41,375)	(5,776)
Accounts payable	25,333	(28,576)
Accrued expenses and other liabilities	(89,393)	(114,353)
Advance billings	35,765	12,092
Increase (Decrease) in Operating Lease Liability	(40,509)	(41,924)
Deferred acquisition related payments	0	(2,855)
Net Cash Provided by (Used in) Operating Activities, Total	54,738	(67,618)
Cash flows from investing activities:
Capitalized software	(29,241)	(17,076)
Capital expenditures	(11,595)	(13,990)
Acquisitions, net of cash acquired	14,172	(20,350)
Other	(8,272)	(767)
Net Cash Provided by (Used in) Investing Activities, Total	(34,936)	(52,183)
Cash flows from financing activities:
Repayment of borrowings under revolving credit facility	(925,000)	(761,000)
Proceeds from borrowings under revolving credit facility	1,038,000	1,036,000
Shares repurchased and cancelled	(67,504)	(86,934)
Distributions to noncontrolling interests	(4,761)	(22,483)
Payment of deferred consideration	(16,103)	(23,963)
Proceeds from (Payments to) Noncontrolling Interests	0	(3,316)
Payments of Financing Costs	(3,570)	0
Net Cash Provided by (Used in) Financing Activities, Total	21,062	138,304
Effect of exchange rate changes on cash and cash equivalents	9,106	(2,162)
Net increase in cash and cash equivalents	49,970	16,341
Cash and cash equivalents at beginning of period	131,339	119,737
Cash and cash equivalents at end of period	181,309	136,078
Supplemental Cash Flow Information:
Cash income taxes paid	14,303	10,636
Cash interest paid	46,800	42,444
Non-cash investing and financing activities:
Acquisitions of business	15,300	7,193
Noncash or Part Noncash Acquisition, Noncontrolling Interest Acquired	0	10,167
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued	0	341
Addition to deferred tax asset related to exchange of Paired Units	204,722	0
Addition to Tax Receivables Agreement liability related to exchange of Paired Units	200,119	0
Conversion of Class C to Class A shares	447,562	0
Non-cash payment on deferred acquisition	$ 0	$ 18,208