Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Income Statement [Abstract]
Revenues	$ 447,662	$ 423,433
Operating costs and expenses:
Costs of services provided	379,691	358,911
Selling, general and administrative expense	44,966	46,911
Other income (expense):
Investment and other income, net	1,284	5,699
Interest expense	(395)	(1,996)
Income before taxes	23,894	21,314
Income tax provision	6,666	6,005
Net income	$ 17,228	$ 15,309
Per share data:
Basic earnings per common share (in dollars per share)	$ 0.23	$ 0.21
Diluted earnings per common share (in dollars per share)	$ 0.23	$ 0.21
Weighted average number of common shares outstanding:
Basic (in shares)	73,670	73,926
Diluted (in shares)	73,961	74,055
Comprehensive income:
Net income	$ 17,228	$ 15,309
Other comprehensive income
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	503	(328)
Total comprehensive income	$ 17,731	$ 14,981