Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Revenues	$ 775,865	$ 702,228	$ 2,254,477	$ 2,099,991
Operating expenses
Direct cost of revenues	526,654	472,235	1,539,838	1,431,381
Selling, general and administrative expenses	159,186	138,600	476,097	399,076
Amortization of intangible assets	2,315	2,860	7,320	8,515
Costs and Expenses	688,155	613,695	2,023,255	1,838,972
Operating income	87,710	88,533	231,222	261,019
Other income (expense)
Interest income and other	7,771	5,175	10,418	5,297
Interest expense	(2,378)	(5,073)	(7,468)	(15,164)
Other income (expense)	5,393	102	2,950	(9,867)
Income before income tax provision	93,103	88,635	234,172	251,152
Income tax provision	15,836	19,155	46,156	54,394
Net income	$ 77,267	$ 69,480	$ 188,016	$ 196,758
Earnings per common share — basic (in dollars per share)	$ 2.29	$ 2.07	$ 5.57	$ 5.88
Earnings per common share — diluted (in dollars per share)	$ 2.15	$ 1.96	$ 5.25	$ 5.58
Other comprehensive loss, net of tax
Foreign currency translation adjustments, net of tax expense of $0	$ (48,475)	$ (18,607)	$ (95,345)	$ (18,042)
Total other comprehensive loss, net of tax	(48,475)	(18,607)	(95,345)	(18,042)
Comprehensive income	$ 28,792	$ 50,873	$ 92,671	$ 178,716