Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Revenues	$ 893,261	$ 775,865	$ 2,564,558	$ 2,254,477
Operating expenses
Direct cost of revenues	598,804	526,654	1,740,407	1,539,838
Selling, general and administrative expenses	186,088	159,186	556,672	476,097
Amortization of intangible assets	1,340	2,315	4,939	7,320
Costs and expenses	786,232	688,155	2,302,018	2,023,255
Operating income	107,029	87,710	262,540	231,222
Other income (expense)
Interest income and other	5,147	7,771	3,221	10,418
Interest expense	(4,474)	(2,378)	(10,435)	(7,468)
Other income (expense)	673	5,393	(7,214)	2,950
Income before income tax provision	107,702	93,103	255,326	234,172
Income tax provision	24,385	15,836	62,067	46,156
Net income	$ 83,317	$ 77,267	$ 193,259	$ 188,016
Earnings per common share — basic (in dollars per share)	$ 2.44	$ 2.29	$ 5.75	$ 5.57
Earnings per common share — diluted (in dollars per share)	$ 2.34	$ 2.15	$ 5.43	$ 5.25
Other comprehensive loss, net of tax
Foreign currency translation adjustments, net of tax expense of $0	$ (18,228)	$ (48,475)	$ (1,982)	$ (95,345)
Total other comprehensive loss, net of tax	(18,228)	(48,475)	(1,982)	(95,345)
Comprehensive income	$ 65,089	$ 28,792	$ 191,277	$ 92,671