Geographic Regions (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									$ 65,463	$ 85,035	$ 100,053
Operating income (loss)	$ (1,181)	$ 31	$ (972)	$ 1,637	$ 1,653	$ 1,351	$ 1,248	$ 664	(485)	4,916	6,072
Net long-lived assets	11,995				10,217				11,995	10,217
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									48,089	65,942	72,753
Operating income (loss)									(5,814)	726	2,755
Net long-lived assets	11,804				9,893				11,804	9,893
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									13,510	9,500	17,634
Operating income (loss)									4,744	3,686	5,445
Net long-lived assets	$ 191				236				191	236
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									3,864	9,593	9,666
Operating income (loss)									$ 585	504	$ (2,128)
Net long-lived assets					$ 88					$ 88