Consolidated Statements of Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Revenues	$ 411,388	$ 414,488	$ 1,247,549	$ 1,266,156
Operating costs and expenses:
Costs of services provided	377,554	376,894	1,106,260	1,129,526
Selling, general and administrative expense	39,047	35,803	120,523	100,820
Other (expense) income:
Investment and other income (loss), net	394	1	7,047	(9,034)
Interest expense	(2,132)	(799)	(5,798)	(1,752)
(Loss) income before income taxes	(6,951)	993	22,015	25,024
Income tax (benefit) provision	(1,457)	671	6,227	6,553
Net (loss) income	$ (5,494)	$ 322	$ 15,788	$ 18,471
Per share data:
Basic (loss) earnings per share (in dollars per share)	$ (0.07)	$ 0.00	$ 0.21	$ 0.25
Diluted (loss) earnings per share (in dollars per share)	$ (0.07)	$ 0.00	$ 0.21	$ 0.25
Weighted average number of common shares outstanding:
Basic (in shares)	74,364	74,340	74,446	74,334
Diluted (in shares)	74,364	74,348	74,496	74,346
Comprehensive (loss) income:
Net (loss) income	$ (5,494)	$ 322	$ 15,788	$ 18,471
Other comprehensive (loss) income:
Unrealized loss on available-for-sale marketable securities, net of taxes	(1,647)	(2,293)	(1,300)	(9,507)
Total comprehensive (loss) income	$ (7,141)	$ (1,971)	$ 14,488	$ 8,964