Supporting Financial Information - Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 48,189	$ 17,623
Less accumulated amortization	(6,981)	(4,258)
Intangible assets, net	$ 41,208	13,365
Finite-lived intangibles estimated useful lives	10 years
Amortization expense of intangibles	$ 2,700	1,800
Customer contracts and related customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	45,600	16,626
Less accumulated amortization	(6,590)	(4,018)
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	480	480
Less accumulated amortization	(164)	(116)
Trade name
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	2,109	517
Less accumulated amortization	$ (227)	$ (124)