Summary of Significant Accounting Policies - Concentration Risk (Details)	3 Months Ended
	Dec. 31, 2017 customer item	Dec. 31, 2016 customer item
Concentration of Credit Risk
Number of banks for maintenance of cash balances	2
Net sales | Major Customers and Products
Concentrations
Number of major customers | customer	1	3
Net sales | Major Customers and Products | S&K Aerospace LLC
Concentrations
Sales percentage	10.00%
Net sales | Major Customers and Products | Sierra Nevada
Concentrations
Sales percentage		32.00%
Net sales | Major Customers and Products | Pilatus
Concentrations
Sales percentage		18.00%
Net sales | Major Customers and Products | DoD
Concentrations
Sales percentage		11.00%
Inventory | Major Suppliers
Concentrations
Number of major suppliers	1	2