Summary of Significant Accounting Policies - Concentration Risk (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2023 item customer	Mar. 31, 2022 item customer	Mar. 31, 2023 customer item	Mar. 31, 2022 customer item
Concentration of Credit Risk
Number of banks for maintenance of cash balances	2		2
Revenues Net | Customer Concentration Risk
Concentrations
Number of major customers | customer	4	3	4	2
Revenues Net | Customer Concentration Risk | Pilatus Aircraft Ltd ("Pilatus")
Concentrations
Concentration of risk (as a percent)	21.00%	29.00%	29.00%	26.00%
Revenues Net | Customer Concentration Risk | Challenge Airlines
Concentrations
Concentration of risk (as a percent)	18.00%		10.00%
Revenues Net | Customer Concentration Risk | Air Transport Services Group
Concentrations
Concentration of risk (as a percent)	16.00%		15.00%	13.00%
Revenues Net | Customer Concentration Risk | Amazon.com Inc
Concentrations
Concentration of risk (as a percent)		11.00%
Revenues Net | Customer Concentration Risk | Textron Aviation, Inc
Concentrations
Concentration of risk (as a percent)	10.00%	10.00%	11.00%
Inventory | Supplier Concentration Risk
Concentrations
Number of major suppliers	3	3	4	3