Income Taxes - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Provision for income taxes attributable to continuing operations
Income tax (benefit) expense at the federal statutory rate	$ (14,720)	$ 878	$ 13,623
State taxes, net of federal benefit	951	184	1,265
Mexico inflation adjustment	(1,120)	(801)	(936)
Non-deductible items	772	2,088	2,214
Tax credits	0	(551)	(615)
Foreign rate differential	(1,671)	1,080	1,405
Change in valuation allowance	962	1,601	3,986
Stock compensation	598	(711)	0
Uncertain tax positions	2,849	(1,596)	(4,808)
Change in tax rate resulting from enactment of the Act	0	0	2,558
Non-deductible impairment	9,093	0	0
Other	654	234	(303)
Total income tax (benefit) expense	$ (1,632)	$ 2,406	$ 18,389
Effective tax rate	2.00%	58.00%	33.00%