Contract Balance - Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Billed	$ 300,179	$ 234,745
Unbilled	213,023	203,896
Receivables Gross	513,202	438,641
Less: allowance for doubtful accounts	(5,806)	(4,978)
Accounts Receivable, after Allowance for Credit Loss	507,396	433,663
Less: long-term receivables	(38,371)	(45,716)
Accounts receivable, net	$ 469,025	$ 387,947