Segment Information - Sales by End Customer (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Total sales	$ 305,259	$ 248,391
U.S. Government
Disaggregation of Revenue
Total sales	169,000
Other
Disaggregation of Revenue
Total sales	136,300
Transportation Systems
Disaggregation of Revenue
Total sales	181,807	146,500
Transportation Systems | U.S. Government
Disaggregation of Revenue
Total sales	90,800
Transportation Systems | Other
Disaggregation of Revenue
Total sales	91,000
Cubic Mission Solutions
Disaggregation of Revenue
Total sales	46,393	33,100
Cubic Mission Solutions | U.S. Government
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 | U.S. Government
Disaggregation of Revenue
Total sales	32,400
Cubic Global Defense | Other
Disaggregation of Revenue
Total sales	$ 44,700