Schedule of Accounts Receivable (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Receivables [Abstract]
Billed and billable	$ 152,686	$ 200,221
Less: allowance for credit losses	(2,060)	(2,760)
Accounts receivable, net	$ 150,626	$ 197,461