Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Statement [Abstract]
Revenues	$ 1,837,173	$ 1,715,682	$ 1,671,389
Operating costs and expenses:
Costs of services provided	1,597,768	1,487,592	1,456,643
Selling, general and administrative expenses	190,866	183,060	166,772
Other income (expense):
Investment and other income, net	20,907	14,349	12,938
Interest expense	(1,580)	(6,438)	(7,856)
Income before taxes	67,866	52,941	53,056
Income tax provision	8,807	13,470	14,670
Net income	$ 59,059	$ 39,471	$ 38,386
Per share data:
Basic earnings per common share (in dollars per share)	$ 0.82	$ 0.54	$ 0.52
Diluted earnings per common share (in dollars per share)	$ 0.81	$ 0.53	$ 0.52
Weighted average number of common shares outstanding:
Basic (in shares)	72,380	73,754	74,288
Diluted (in shares)	73,032	73,988	74,340
Comprehensive income:
Net income	$ 59,059	$ 39,471	$ 38,386
Other comprehensive income (loss)
Unrealized gain on available-for-sale marketable securities, net of taxes	1,869	(473)	1,633
Total comprehensive income	$ 60,928	$ 38,998	$ 40,019