Supporting Financial Information - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 48,189		$ 48,189
Total accumulated amortization	(8,185)		(6,981)
Intangible assets, net	$ 40,004		41,208
Estimated useful live of intangible assets	10 years
Amortization expense of intangible assets	$ 1,200	$ 400
Customer contracts and related customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	45,600		45,600
Total accumulated amortization	(7,730)		(6,590)
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	480		480
Total accumulated amortization	(176)		(164)
Trade name
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	2,109		2,109
Total accumulated amortization	$ (279)		$ (227)