Segment Information - Revenue Recognition Method (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue
Total sales	$ 382,679	$ 296,212	$ 1,025,277	$ 823,189
Point in time
Disaggregation of Revenue
Total sales	106,700		240,300
Over time
Disaggregation of Revenue
Total sales	276,000		785,000
Transportation Systems
Disaggregation of Revenue
Total sales	212,672	164,600	595,172	478,100
Transportation Systems | Point in time
Disaggregation of Revenue
Total sales	29,700		68,200
Transportation Systems | Over time
Disaggregation of Revenue
Total sales	183,000		527,000
Cubic Mission Solutions
Disaggregation of Revenue
Total sales	94,978	42,700	203,306	111,900
Cubic Mission Solutions | Point in time
Disaggregation of Revenue
Total sales	76,000		169,200
Cubic Mission Solutions | Over time
Disaggregation of Revenue
Total sales	19,000		34,100
Cubic Global Defense
Disaggregation of Revenue
Total sales	75,029	$ 88,900	226,799	$ 233,200
Cubic Global Defense | Point in time
Disaggregation of Revenue
Total sales	1,000		2,900
Cubic Global Defense | Over time
Disaggregation of Revenue
Total sales	$ 74,000		$ 223,900