Goodwill and Other Intangible Assets - Definite-lived Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	$ 68,597	$ 47,675
Accumulated Amortization	(30,008)	(23,055)
Net Book Value	38,589	24,620
Definite-lived intangible assets, amortization expense	7,800	5,800	$ 4,200
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	3,563	3,626
Accumulated Amortization	(3,399)	(3,314)
Net Book Value	164	312
Internally developed software
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	59,436	40,223
Accumulated Amortization	(24,280)	(17,512)
Net Book Value	35,156	22,711
Other
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	5,598	3,826
Accumulated Amortization	(2,329)	(2,229)
Net Book Value	$ 3,269	$ 1,597