Supporting Financial Information - Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	$ 164,542	$ 164,542
Total accumulated amortization	(52,107)	(39,765)
Intangible assets, net	112,435	124,777
Customer contracts and related customer relationships
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	113,622	113,622
Total accumulated amortization	(38,455)	(29,929)
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	637	637
Total accumulated amortization	(426)	(378)
Trade name
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	13,034	13,034
Total accumulated amortization	(3,162)	(2,185)
Backlog
Finite-Lived Intangible Assets [Line Items]
Total intangible assets	37,249	37,249
Total accumulated amortization	$ (10,064)	$ (7,273)