Segment Information - Business segment financial data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Information
Total sales	$ 382,679	$ 296,212	$ 1,025,277	$ 823,189
Operating income (loss)	34,725	10,290	27,618	(3,291)
Total depreciation and amortization	15,351	10,642	48,949	34,133
Transportation Systems
Segment Information
Total sales	212,672	164,600	595,172	478,100
Operating income (loss)	17,277	18,600	37,048	42,700
Total depreciation and amortization	6,900	2,800	24,100	9,100
Cubic Mission Solutions
Segment Information
Total sales	94,978	42,700	203,306	111,900
Operating income (loss)	1,230	(500)	(12,133)	(17,200)
Total depreciation and amortization	6,000	4,700	17,200	15,800
Cubic Global Defense
Segment Information
Total sales	75,029	88,900	226,799	233,200
Operating income (loss)	1,928	6,900	9,998	13,600
Total depreciation and amortization	1,700	2,000	5,400	6,100
Corporate
Segment Information
Total depreciation and amortization	700	1,100	2,200	3,100
Unallocated corporate expenses and other
Segment Information
Operating income (loss)	$ 14,290	$ (14,700)	$ (7,295)	$ (42,400)