Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenues	$ 864,591	$ 754,992	$ 1,671,297	$ 1,478,612
Operating expenses
Direct cost of revenues	588,094	520,080	1,141,603	1,013,184
Selling, general and administrative expenses	186,371	167,940	370,584	316,911
Amortization of intangible assets	1,417	2,737	3,599	5,005
Costs and expenses	775,882	690,757	1,515,786	1,335,100
Operating income	88,709	64,235	155,511	143,512
Other income (expense)
Interest income and other	(584)	2,994	(1,926)	2,647
Interest expense	(3,022)	(2,448)	(5,961)	(5,090)
Other income (expense)	(3,606)	546	(7,887)	(2,443)
Income before income tax provision	85,103	64,781	147,624	141,069
Income tax provision	22,708	13,353	37,682	30,320
Net income	$ 62,395	$ 51,428	$ 109,942	$ 110,749
Earnings per common share — basic (in dollars per share)	$ 1.87	$ 1.52	$ 3.30	$ 3.29
Earnings per common share — diluted (in dollars per share)	$ 1.75	$ 1.43	$ 3.09	$ 3.10
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments, net of tax expense of $0	$ 6,396	$ (40,679)	$ 16,246	$ (46,870)
Total other comprehensive income (loss), net of tax	6,396	(40,679)	16,246	(46,870)
Comprehensive income	$ 68,791	$ 10,749	$ 126,188	$ 63,879