Segment Information - Sales by Deliverable Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue
Sales	$ 350,439	$ 382,679	$ 1,000,760	$ 1,025,277
Products
Disaggregation of Revenue
Sales	221,039	255,900	609,137	660,897
Services
Disaggregation of Revenue
Sales	129,400	126,779	391,623	364,380
Cubic Transportation Systems
Disaggregation of Revenue
Sales	215,500	212,700	601,800	595,200
Cubic Transportation Systems | Products
Disaggregation of Revenue
Sales	124,200	122,800	317,400	328,700
Cubic Transportation Systems | Services
Disaggregation of Revenue
Sales	91,300	89,900	284,400	266,500
Cubic Mission Solutions
Disaggregation of Revenue
Sales	69,000	95,000	167,200	203,300
Cubic Mission Solutions | Products
Disaggregation of Revenue
Sales	59,700	87,300	141,600	183,900
Cubic Mission Solutions | Services
Disaggregation of Revenue
Sales	9,300	7,700	25,600	19,400
Cubic Global Defense Systems
Disaggregation of Revenue
Sales	65,900	75,000	231,800	226,800
Cubic Global Defense Systems | Products
Disaggregation of Revenue
Sales	37,100	45,800	150,200	148,300
Cubic Global Defense Systems | Services
Disaggregation of Revenue
Sales	$ 28,800	$ 29,200	$ 81,600	$ 78,500