Accounts Receivable - Schedule of Total Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 30, 2020
Accounts Receivable Net [Abstract]
Billed and billable receivables	$ 668,563	$ 779,339
Unbilled receivables	79,282	61,888
Total accounts receivable, net – current	747,845	841,227
Unbilled receivables, long-term	11,248	9,629
Total accounts receivable	$ 759,093	$ 850,856