Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Revenues	$ 723,620	$ 686,277
Operating expenses
Direct cost of revenues	493,104	468,424
Selling, general and administrative expenses	148,971	126,546
Amortization of intangible assets	2,268	2,801
Costs and Expenses	644,343	597,771
Operating income	79,277	88,506
Other income (expense)
Interest income and other	(347)	1,034
Interest expense	(2,642)	(4,797)
Other income (expense)	(2,989)	(3,763)
Income before income tax provision	76,288	84,743
Income tax provision	16,967	20,247
Net income	$ 59,321	$ 64,496
Earnings per common share — basic (in dollars per share)	$ 1.76	$ 1.93
Earnings per common share — diluted (in dollars per share)	$ 1.66	$ 1.84
Other comprehensive loss, net of tax
Foreign currency translation adjustments, net of tax expense of $0	$ (6,191)	$ (5,242)
Total other comprehensive loss, net of tax	(6,191)	(5,242)
Comprehensive income	$ 53,130	$ 59,254