Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Intangible Assets
Goodwill impairment charges	$ 0	$ 0	$ 0
Change to goodwill	0
Amortization of customer relationships, patents, non-competes and other intangibles	527	496	$ 503
Total intangible assets, Gross Amount	10,221	10,221
Finite-lived intangible assets, Accumulated Amortization	(4,682)	(4,155)
Carrying Amount	$ 5,539	6,066
Minimum
Intangible Assets
Useful life	2 years
Maximum
Intangible Assets
Useful life	16 years
Patents
Intangible Assets
Finite-lived intangible assets Gross Amount	$ 4,030	4,030
Finite-lived intangible assets, Accumulated Amortization	(3,977)	(3,656)
Finite-lived intangible assets, Carrying Amount	53	374
Customer relationships
Intangible Assets
Finite-lived intangible assets Gross Amount	2,100	2,100
Finite-lived intangible assets, Accumulated Amortization	(574)	(426)
Finite-lived intangible assets, Carrying Amount	1,526	1,674
Other Intangible Assets
Intangible Assets
Finite-lived intangible assets Gross Amount	291	291
Finite-lived intangible assets, Accumulated Amortization	(131)	(73)
Finite-lived intangible assets, Carrying Amount	160	218
Trademarks
Intangible Assets
Indefinite-lived intangible assets	$ 3,800	$ 3,800