Revenue Recognition - Schedule of Net Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Billed	$ 1,934,300	$ 2,184,900
Contract retentions	647,600	696,300
Total accounts receivable—gross	2,581,900	2,881,200
Allowance for doubtful accounts and credit losses	(84,800)	(87,900)
Total accounts receivable—net	$ 2,497,147	$ 2,793,307