Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net income	$ 235,514	$ 234,966	$ 210,682
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35,898	34,269	32,661
Amortization and impairment of intangible assets	9,643	10,823	10,387
Acquisition-related contingent consideration	2,172	(324)	5,593
Provision for expected credit losses	19,684	16,151	19,692
Share-based compensation	25,414	23,051	22,904
Amortization of debt discount and issuance costs and other	2,224	11,701	11,259
Deferred income taxes	(10,456)	4,958	(9,132)
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, billed and unbilled	(182,667)	(61,274)	(26,800)
Notes receivable	(403)	12,645	8,029
Prepaid expenses and other assets	459	(1,165)	4,640
Accounts payable, accrued expenses and other	8,430	(2,102)	13,901
Income taxes	(4,322)	10,523	(22,549)
Accrued compensation	37,931	59,566	38,627
Billings in excess of services provided	9,273	1,695	7,175
Net cash provided by operating activities	188,794	355,483	327,069
Investing activities
Payments for acquisition of businesses, net of cash received	(6,742)	(10,428)	(25,271)
Purchases of property and equipment and other	(53,319)	(68,665)	(34,849)
Net cash used in investing activities	(60,061)	(79,093)	(60,120)
Financing activities
Borrowings under revolving line of credit	165,000	402,500	289,500
Repayments under revolving line of credit	(165,000)	(402,500)	(289,500)
Payments of debt issuance costs	(3,993)	0	0
Purchase and retirement of common stock	(85,424)	(46,133)	(353,593)
Share-based compensation tax withholdings and other	(15,330)	(9,246)	(5,823)
Payments for business acquisition liabilities	(4,848)	(7,496)	(3,948)
Deposits and other	3,583	1,201	3,311
Net cash used in financing activities	(106,012)	(61,674)	(360,053)
Effect of exchange rate changes on cash and cash equivalents	(25,518)	(15,184)	18,684
Net increase (decrease) in cash and cash equivalents	(2,797)	199,532	(74,420)
Cash and cash equivalents, beginning of period	494,485	294,953	369,373
Cash and cash equivalents, end of period	491,688	494,485	294,953
Supplemental cash flow disclosures
Cash paid for interest	7,836	9,102	7,752
Cash paid for income taxes, net of refunds	77,013	47,500	83,445
Non-cash investing and financing activities:
Issuance of stock units under incentive compensation plans	1,664	2,603	2,314
Business acquisition liabilities not yet paid	5,593	1,093	6,209
Non-cash additions to property and equipment	$ 4,272	$ 6,518	$ 4,966