UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	$ (12,145)	$ 93,415
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Stock-based compensation	34,615	33,410
Depreciation and amortization	107,795	95,642
Impairment and other losses	10,562	28,034
Deferred income taxes	(1,112)	(1,557)
Adjustment To Deferred Acquisition Consideration	10,881	(14,420)
Other, net	(4,292)	1,679
Changes in working capital:
Accounts receivable	(25,405)	(34,637)
Expenditures billable to clients	(36,217)	5,525
Other assets	6,539	4,100
Accounts payable	(58,716)	34,630
Accrued expenses and other liabilities	(149,267)	(138,947)
Advance billings	(1,759)	(23,017)
Deferred acquisition related payments	(9,021)	(10,776)
Net Cash Provided by (Used in) Operating Activities, Total	(127,542)	73,081
Cash flows from investing activities:
Capital expenditures	(12,205)	(16,103)
Acquisitions, net of cash acquired	(6,678)	(37,461)
Capitalized software	(19,026)	(9,392)
Other	(6,939)	(1,328)
Net Cash Provided by (Used in) Investing Activities, Total	(44,848)	(64,284)
Cash flows from financing activities:
Repayment of borrowings under revolving credit facility	(1,250,500)	(855,000)
Proceeds from borrowings under revolving credit facility	1,562,500	989,500
Shares repurchased and cancelled	(203,958)	(43,637)
Distributions to noncontrolling interests	(24,538)	(38,486)
Payment of deferred consideration	(31,666)	(61,089)
Purchase of noncontrolling interest	0	(3,600)
Debt issuance costs	(150)	0
Net Cash Provided by (Used in) Financing Activities, Total	51,688	(12,312)
Effect of exchange rate changes on cash and cash equivalents	(1,182)	(15,243)
Net decrease in cash and cash equivalents	(121,884)	(18,758)
Cash and cash equivalents at beginning of period	220,589	184,009
Cash and cash equivalents at end of period	98,705	165,251
Supplemental Cash Flow Information:
Cash income taxes paid	40,088	23,315
Cash interest paid	63,878	61,016
Non-cash investing and financing activities:
Establishment of Tax Receivables Agreement liability	0	17,649
Non-cash payment on deferred acquisition	20,119	0
Establishment of a deferred tax asset related to the exchange	$ 0	$ 20,763