Revenue - Contract Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2024	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Contract assets	$ 75,010	$ 60,621
Contract liabilities	(315,699)	(279,796)
Net contract liability	(240,689)	$ (219,175)
Revenue recognized related to contract liabilities	185,400
Retention amounts included in accounts receivable	7,400
Retained amount expected to be collected in the next twelve months	7,100
Retained amount expected to be collected	$ 300