Restructuring Costs - Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring plan
Restructuring costs	$ 3,393	$ 8,505	$ 8,775	$ 12,254
Unallocated corporate expenses
Restructuring plan
Restructuring costs	2,100	4,500	6,400	7,400
Cubic Transportation Systems
Restructuring plan
Restructuring costs	200	1,400	700	2,200
Cubic Mission Solutions
Restructuring plan
Restructuring costs	400		400
Cubic Global Defense Systems
Restructuring plan
Restructuring costs	$ 700	$ 2,600	$ 1,300	$ 2,700