Restructuring Costs - Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Restructuring plan
Restructuring costs	$ 3,807	$ 1,757	$ 5,382	$ 3,749
Unallocated corporate expenses and other
Restructuring plan
Restructuring costs	3,200	1,400	4,300	2,900
Cubic Transportation Systems
Restructuring plan
Restructuring costs	100	$ 300	500	700
Cubic Global Defense Systems
Restructuring plan
Restructuring costs	$ 500		$ 600	$ 100