Consolidated Statements of Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Revenues	$ 426,288	$ 418,931	$ 849,721	$ 836,161
Operating costs and expenses:
Costs of services provided	384,742	368,204	743,653	730,583
Selling, general and administrative expense	44,437	41,429	91,348	81,476
Other income (expense):
Investment and other income, net	2,621	3,551	8,320	6,653
Interest expense	(1,716)	(1,915)	(3,712)	(3,666)
(Loss) income before taxes	(1,986)	10,934	19,328	27,089
Income tax (benefit) provision	(198)	2,680	5,807	7,164
Net (loss) income	$ (1,788)	$ 8,254	$ 13,521	$ 19,925
Per share data:
Basic (loss) earnings per common share (in dollars per share)	$ (0.02)	$ 0.11	$ 0.18	$ 0.27
Diluted (loss) earnings per common share (in dollars per share)	$ (0.02)	$ 0.11	$ 0.18	$ 0.27
Weighted average number of common shares outstanding:
Basic (in shares)	73,853	74,478	73,889	74,488
Diluted (in shares)	73,853	74,567	74,048	74,543
Comprehensive (loss) income:
Net (loss) income	$ (1,788)	$ 8,254	$ 13,521	$ 19,925
Other comprehensive (loss) income
Unrealized (loss) gain on available-for-sale marketable securities, net of taxes	(445)	(860)	(773)	347
Total comprehensive (loss) income	$ (2,233)	$ 7,394	$ 12,748	$ 20,272