Supporting Financial Information - Intangible Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 164,542	$ 164,542
Accumulated amortization	(56,221)	(39,765)
Intangible assets, net	108,321	124,777
Customer contracts and related customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	113,622	113,622
Accumulated amortization	(41,297)	(29,929)
Backlog
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	37,249	37,249
Accumulated amortization	(10,994)	(7,273)
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	13,034	13,034
Accumulated amortization	(3,488)	(2,185)
Covenants-not-to-compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	637	637
Accumulated amortization	$ (442)	$ (378)