Accounts Receivable - Schedule of Total Accounts Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020
Accounts Receivable Net [Abstract]
Billed and billable receivables	$ 729,450	$ 779,339
Unbilled receivables	90,707	61,888
Total accounts receivable, net – current	820,157	841,227
Unbilled receivables, long-term	9,611	9,629
Total accounts receivable	$ 829,768	$ 850,856