Segment Information - Sales by Deliverable Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue
Sales	$ 328,839	$ 305,259
Products
Disaggregation of Revenue
Sales	200,604	182,253
Services
Disaggregation of Revenue
Sales	128,235	123,006
Cubic Transportation Systems
Disaggregation of Revenue
Sales	188,600	181,800
Cubic Transportation Systems | Products
Disaggregation of Revenue
Sales	93,400	92,000
Cubic Transportation Systems | Services
Disaggregation of Revenue
Sales	95,200	89,800
Cubic Mission Solutions
Disaggregation of Revenue
Sales	58,700	46,400
Cubic Mission Solutions | Products
Disaggregation of Revenue
Sales	51,200	40,600
Cubic Mission Solutions | Services
Disaggregation of Revenue
Sales	7,500	5,800
Cubic Global Defense Systems
Disaggregation of Revenue
Sales	81,500	77,100
Cubic Global Defense Systems | Products
Disaggregation of Revenue
Sales	56,000	49,700
Cubic Global Defense Systems | Services
Disaggregation of Revenue
Sales	$ 25,500	$ 27,400