Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Revenues	$ 754,992	$ 711,486	$ 1,478,612	$ 1,397,763
Operating expenses
Direct cost of revenues	520,080	490,722	1,013,184	959,146
Selling, general and administrative expenses	167,940	133,930	316,911	260,476
Amortization of intangible assets	2,737	2,854	5,005	5,655
Costs and Expenses	690,757	627,506	1,335,100	1,225,277
Operating income	64,235	83,980	143,512	172,486
Other income (expense)
Interest income and other	2,994	(912)	2,647	122
Interest expense	(2,448)	(5,294)	(5,090)	(10,091)
Other income (expense)	546	(6,206)	(2,443)	(9,969)
Income before income tax provision	64,781	77,774	141,069	162,517
Income tax provision	13,353	14,992	30,320	35,239
Net income	$ 51,428	$ 62,782	$ 110,749	$ 127,278
Earnings per common share — basic (in dollars per share)	$ 1.52	$ 1.88	$ 3.29	$ 3.80
Earnings per common share — diluted (in dollars per share)	$ 1.43	$ 1.77	$ 3.10	$ 3.61
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments, net of tax expense of $0	$ (40,679)	$ 5,807	$ (46,870)	$ 565
Total other comprehensive income (loss), net of tax	(40,679)	5,807	(46,870)	565
Comprehensive income	$ 10,749	$ 68,589	$ 63,879	$ 127,843