Concentrations (Details) $ in Millions	12 Months Ended
	Sep. 30, 2021 USD ($) customer item	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)
Flat Panel Display Systems
Concentrations
Concentration Risk Threshold Percentage	88.00%	80.00%	90.00%
Concentration of Credit Risk
Concentration of Credit Risk
Number of banks for maintenance of cash balances	2
Revenues Net | Customer Concentration Risk
Concentrations
Number of major customers | customer	5
Concentration Risk Threshold Percentage	59.00%	63.00%	53.00%
Revenues Net | Customer Concentration Risk | Pilatus
Concentrations
Concentration Risk Threshold Percentage	20.00%	33.00%	25.00%
Revenues Net | Customer Concentration Risk | Government Contractors and Agencies
Concentrations
Concentration Risk Threshold Percentage	18.00%	32.00%	20.00%
Revenues Net | Product Concentration Risk | Flat Panel Display Systems
Concentrations
Concentration Risk Threshold Percentage	88.00%	80.00%	90.00%
Revenues Net | Product Concentration Risk | Air Data Systems and Components
Concentrations
Concentration Risk Threshold Percentage	12.00%	20.00%	10.00%
Accounts receivable | Customer Concentration Risk
Concentrations
Concentration Risk Threshold Percentage	5.00%
Accounts receivable and contract assets | $	$ 2.1	$ 3.4	$ 1.3
Inventory | Supplier Concentration Risk
Concentrations
Concentration Risk Threshold Percentage	14.90%	32.80%
Number of major suppliers	1	2