Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 26,207	$ 29,067
North America
Disaggregation of Revenue [Line Items]
Revenue	23,776	25,721
Europe
Disaggregation of Revenue [Line Items]
Revenue	2,431	3,346
Commercial revenue
Disaggregation of Revenue [Line Items]
Revenue	10,191	12,067
Military revenue
Disaggregation of Revenue [Line Items]
Revenue	16,016	17,000
Fixed wing aircraft
Disaggregation of Revenue [Line Items]
Revenue	11,335	13,304
Rotorcraft
Disaggregation of Revenue [Line Items]
Revenue	6,848	5,130
Energy components for power generation units
Disaggregation of Revenue [Line Items]
Revenue	2,658	3,732
Commercial product and other revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 5,366	$ 6,901
Transferred over Time | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk	61.00%