Segment Information - Sales by Deliverable Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue
Total sales	$ 337,339	$ 278,586	$ 642,598	$ 526,977
Products
Disaggregation of Revenue
Total sales	222,744	157,445	404,997	289,188
Services
Disaggregation of Revenue
Total sales	114,595	121,141	237,601	237,789
Transportation Systems
Disaggregation of Revenue
Total sales	200,693	167,000	382,500	313,500
Transportation Systems | Products
Disaggregation of Revenue
Total sales	113,800		205,800
Transportation Systems | Services
Disaggregation of Revenue
Total sales	86,900		176,700
Cubic Mission Solutions
Disaggregation of Revenue
Total sales	61,935	36,100	108,328	69,200
Cubic Mission Solutions | Products
Disaggregation of Revenue
Total sales	56,100		96,700
Cubic Mission Solutions | Services
Disaggregation of Revenue
Total sales	5,800		11,600
Cubic Global Defense
Disaggregation of Revenue
Total sales	74,711	$ 75,500	151,770	$ 144,300
Cubic Global Defense | Products
Disaggregation of Revenue
Total sales	52,800		102,500
Cubic Global Defense | Services
Disaggregation of Revenue
Total sales	$ 21,900		$ 49,300