Restructuring Costs - Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restructuring plan
Restructuring costs	$ 4,135	$ 1,575
Unallocated corporate expenses
Restructuring plan
Restructuring costs	800	1,100
Cubic Transportation Systems
Restructuring plan
Restructuring costs	200	400
Cubic Mission and Performance Solutions
Restructuring plan
Restructuring costs	$ 3,100	$ 100