Segment Information - Sales by Contract Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Total sales	$ 305,259	$ 248,391
Fixed Price
Disaggregation of Revenue
Total sales	295,600
Other
Disaggregation of Revenue
Total sales	9,700
Transportation Systems
Disaggregation of Revenue
Total sales	181,807	146,500
Transportation Systems | Fixed Price
Disaggregation of Revenue
Total sales	178,200
Transportation Systems | Other
Disaggregation of Revenue
Total sales	3,600
Cubic Mission Solutions
Disaggregation of Revenue
Total sales	46,393	33,100
Cubic Mission Solutions | Fixed Price
Disaggregation of Revenue
Total sales	45,800
Cubic Mission Solutions | Other
Disaggregation of Revenue
Total sales	600
Cubic Global Defense
Disaggregation of Revenue
Total sales	77,059	$ 68,800
Cubic Global Defense | Fixed Price
Disaggregation of Revenue
Total sales	71,600
Cubic Global Defense | Other
Disaggregation of Revenue
Total sales	$ 5,500