Restructuring - Restructuring charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Restructuring plan
Expected remaining restructuring costs	$ 900
Restructuring costs	15,386	$ 5,018	$ 2,260
Unallocated corporate expenses and other
Restructuring plan
Restructuring costs	8,900	3,100	1,000
Cubic Transportation Systems
Restructuring plan
Restructuring costs	3,200	400	400
Cubic Mission Solutions
Restructuring plan
Restructuring costs		200
Cubic Global Defense
Restructuring plan
Restructuring costs	$ 3,300	$ 1,300	$ 900