Revenue Recognition - Schedule of Net Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Billed	$ 2,039,900	$ 2,184,900
Contract retentions	696,400	696,300
Total accounts receivable—gross	2,736,300	2,881,200
Allowance for doubtful accounts and credit losses	(87,300)	(87,900)
Total accounts receivable—net	$ 2,648,977	$ 2,793,307