Segment Information - Business segment financial data (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($) item
Revenue recognition
Number of Operating Segments | item				3
Sales	$ 343,709	$ 366,024	$ 678,386	$ 679,837
Operating income (Loss)	(2,072)	(9,086)	(6,173)	(17,163)
Depreciation and amortization	12,292	10,029	25,736	18,977
Transportation Systems
Revenue recognition
Sales	139,600	148,700	271,500	274,500
Operating income (Loss)	7,800	19,800	17,500	23,400
Depreciation and amortization	2,000	1,700	4,400	4,200
Defense Systems
Revenue recognition
Sales	108,400	116,300	220,900	212,200
Operating income (Loss)	(4,400)	(21,200)	(4,900)	(24,600)
Depreciation and amortization	7,700	6,900	16,500	11,000
Cubic Global Defense Services
Revenue recognition
Sales	95,700	101,000	186,000	193,100
Operating income (Loss)	2,000	4,300	1,600	4,500
Depreciation and amortization	700	1,000	1,700	3,000
Corporate and other
Revenue recognition
Depreciation and amortization	1,900	400	3,100	800
Unallocated corporate expenses and other
Revenue recognition
Operating income (Loss)	$ (7,500)	$ (12,000)	$ (20,400)	$ (20,500)