Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenues	$ 418,931	$ 424,857	$ 836,161	$ 851,668
Operating costs and expenses:
Costs of services provided	367,728	379,370	728,706	752,632
Selling, general and administrative expense	41,429	29,281	81,476	65,017
Other income (expense):
Investment and other income (loss), net	3,551	(7,511)	6,653	(9,034)
Interest expense	(1,915)	(445)	(3,666)	(954)
Income before income taxes	11,410	8,250	28,966	24,031
Income tax provision	2,812	1,430	7,684	5,882
Net income	$ 8,598	$ 6,820	$ 21,282	$ 18,149
Per share data:
Basic earnings per common share (in dollars per share)	$ 0.12	$ 0.09	$ 0.29	$ 0.24
Diluted earnings per common share (in dollars per share)	$ 0.12	$ 0.09	$ 0.29	$ 0.24
Weighted average number of common shares outstanding:
Basic (in shares)	74,478	74,337	74,488	74,332
Diluted (in shares)	74,567	74,358	74,543	74,345
Comprehensive income:
Net income	$ 8,598	$ 6,820	$ 21,282	$ 18,149
Other comprehensive (loss) gain:
Unrealized (loss) gain on available-for-sale marketable securities, net of taxes	(860)	(1,945)	347	(7,214)
Total comprehensive income	$ 7,738	$ 4,875	$ 21,629	$ 10,935