Segment Information - Sales by Deliverable Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue
Sales	$ 321,482	$ 337,339	$ 650,321	$ 642,598
Products
Disaggregation of Revenue
Sales	187,494	222,744	388,098	404,997
Services
Disaggregation of Revenue
Sales	133,988	114,595	262,223	237,601
Cubic Transportation Systems
Disaggregation of Revenue
Sales	197,600	200,700	386,200	382,500
Cubic Transportation Systems | Products
Disaggregation of Revenue
Sales	99,700	113,800	193,100	205,800
Cubic Transportation Systems | Services
Disaggregation of Revenue
Sales	97,900	86,900	193,100	176,700
Cubic Mission Solutions
Disaggregation of Revenue
Sales	39,500	61,900	98,200	108,300
Cubic Mission Solutions | Products
Disaggregation of Revenue
Sales	30,700	56,100	81,900	96,700
Cubic Mission Solutions | Services
Disaggregation of Revenue
Sales	8,800	5,800	16,300	11,600
Cubic Global Defense Systems
Disaggregation of Revenue
Sales	84,400	74,700	165,900	151,800
Cubic Global Defense Systems | Products
Disaggregation of Revenue
Sales	57,100	52,800	113,100	102,500
Cubic Global Defense Systems | Services
Disaggregation of Revenue
Sales	$ 27,300	$ 21,900	$ 52,800	$ 49,300