Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Revenues	$ 1,715,682	$ 1,671,389	$ 1,690,176
Operating costs and expenses:
Costs of services provided	1,487,592	1,456,643	1,496,865
Selling, general and administrative expense	183,060	166,772	140,344
Other income (expense):
Investment and other income (loss), net	14,349	12,938	(5,427)
Interest expense	(6,438)	(7,856)	(2,987)
Income before taxes	52,941	53,056	44,553
Income tax provision	13,470	14,670	10,310
Net income	$ 39,471	$ 38,386	$ 34,243
Per share data:
Basic earnings per common share (in dollars per share)	$ 0.54	$ 0.52	$ 0.46
Diluted earnings per common share (in dollars per share)	$ 0.53	$ 0.52	$ 0.46
Weighted average number of common shares outstanding:
Basic (in shares)	73,754	74,288	74,336
Diluted (in shares)	73,988	74,340	74,351
Comprehensive income:
Net income	$ 39,471	$ 38,386	$ 34,243
Other comprehensive (loss) income
Unrealized (loss) gain on available-for-sale marketable securities, net of taxes	(473)	1,633	(7,477)
Total comprehensive income	$ 38,998	$ 40,019	$ 26,766