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Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 871,155	$ 620,228	$ 1,729,353	$ 1,335,330
Top client
Disaggregation of Revenue [Line Items]
Revenue	110,356	74,932	274,650	156,199
Clients 2-5
Disaggregation of Revenue [Line Items]
Revenue	246,094	179,018	475,994	381,996
Clients 6-10
Disaggregation of Revenue [Line Items]
Revenue	116,237	86,449	239,130	160,800
Clients 11-25
Disaggregation of Revenue [Line Items]
Revenue	158,577	101,417	296,432	231,501
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 239,891	$ 178,412	$ 443,147	$ 404,834

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

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