Revenue - Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Contract assets	$ 67,904	$ 54,199
Contract liabilities	(49,396)	(42,433)
Net contract asset	18,508	11,766
Revenue recognized related to contract liabilities	23,300
Retention amounts included in accounts receivable	9,300	$ 9,600
Retained amount expected to be collected in the next twelve months	6,800
Retained amount expected to be collected	$ 2,500