Segment Information - Business segment financial data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Information
Sales	$ 296,212	$ 266,184	$ 823,189	$ 758,594
Operating income (loss)	10,290	(6,848)	(3,291)	(18,579)
Depreciation and amortization	10,642	11,750	34,133	35,774
Transportation Systems
Segment Information
Sales	164,600	136,400	478,100	407,900
Operating income (loss)	18,600	(900)	42,700	16,500
Depreciation and amortization	2,800	2,400	9,100	6,900
Defense Systems
Segment Information
Sales	88,900	89,100	233,200	247,400
Operating income (loss)	6,900	10,400	13,600	18,400
Depreciation and amortization	2,000	3,500	6,100	7,300
Cubic Mission Solutions
Segment Information
Sales	42,700	40,700	111,900	103,300
Operating income (loss)	(500)	(1,500)	(17,200)	(14,500)
Depreciation and amortization	4,700	5,400	15,800	18,100
Corporate
Segment Information
Depreciation and amortization	1,100	500	3,100	3,500
Unallocated corporate expenses and other
Segment Information
Operating income (loss)	$ (14,700)	$ (14,800)	$ (42,400)	$ (39,000)