Supporting Financial Information - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 17,623		$ 17,623		$ 17,623
Total accumulated amortization	(3,818)		(3,818)		(2,496)
Intangible assets, net	13,805		$ 13,805		15,127
Estimated useful live of intangible assets			10 years
Amortization expense of intangible assets	400	$ 400	$ 1,300	$ 1,000
Customer contracts and related customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	16,626		16,626		16,626
Total accumulated amortization	(3,602)		(3,602)		(2,355)
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	480		480		480
Total accumulated amortization	(104)		(104)		(68)
Trade name
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	517		517		517
Total accumulated amortization	$ (112)		$ (112)		$ (73)