Schedule of Accounts Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Receivables [Abstract]
Billed and billable	$ 126,118	$ 200,221
Less: allowance for credit losses	(2,370)	(2,760)
Accounts receivable, net	$ 123,748	$ 197,461

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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