Segment Information - Sales by Deliverable Type (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
Products
Disaggregation of Revenue
Total sales	255,900	179,761	660,897	468,949
Services
Disaggregation of Revenue
Total sales	126,779	116,451	364,380	354,240
Transportation Systems
Disaggregation of Revenue
Total sales	212,672	164,600	595,172	478,100
Transportation Systems | Products
Disaggregation of Revenue
Total sales	122,800		328,700
Transportation Systems | Services
Disaggregation of Revenue
Total sales	89,900		266,500
Cubic Mission Solutions
Disaggregation of Revenue
Total sales	94,978	42,700	203,306	111,900
Cubic Mission Solutions | Products
Disaggregation of Revenue
Total sales	87,300		183,900
Cubic Mission Solutions | Services
Disaggregation of Revenue
Total sales	7,700		19,400
Cubic Global Defense
Disaggregation of Revenue
Total sales	75,029	$ 88,900	226,799	$ 233,200
Cubic Global Defense | Products
Disaggregation of Revenue
Total sales	45,800		148,300
Cubic Global Defense | Services
Disaggregation of Revenue
Total sales	$ 29,200		$ 78,500