BUSINESS SEGMENT INFORMATION - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended									12 Months Ended
	Aug. 31, 2015 USD ($)	Sep. 30, 2014 item	Sep. 30, 2016 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($)	Sep. 30, 2016 USD ($) item $ / shares	Sep. 30, 2015 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares
Revenue recognition
Increase (decrease) in operating income			$ 10,488	$ 13,893	$ (9,086)	$ (8,077)	$ 34,709	$ 10,293	$ 23,206	$ 7,179		$ 7,218	$ 75,387	$ 92,490
Increase (decrease) in net income												$ 1,735	$ 22,914	$ 69,580
Increase (decrease) in net income per common share (in dollars per share) | $ / shares			$ (0.29)	$ 0.17	$ 0.38	$ (0.20)	$ 0.74	$ 0.33	$ (0.41)	$ 0.19		$ 0.06	$ 0.85	$ 2.59
Sales related to annual system usage incentives	$ 3,100								$ 9,300		$ 12,200
Restructuring costs												$ 1,852	$ 6,272	$ 1,094
Cubic Transportation Systems
Revenue recognition
Sales to Transport for London												156,300	183,200	213,200
Increase (decrease) in operating income												57,500	75,900	65,900
Restructuring costs												$ 1,000	600	700
Reduction in employee headcount | item		20										20
Cubic Global Defense Systems
Revenue recognition
Increase (decrease) in operating income												$ (17,100)	18,400	26,800
Restructuring costs												300	4,600	500
Cubic Global Defense Services
Revenue recognition
Increase (decrease) in operating income												11,200	6,600	7,800
Restructuring costs												600	600
CGD services and CGD systems segments
Revenue recognition
Sales to U.S. government agencies												657,900	670,000	651,100
Restructuring costs												900
Unallocated corporate expenses and other
Revenue recognition
Increase (decrease) in operating income												(44,400)	(25,500)	(8,000)
Restructuring costs													500	(100)
Change in estimated total costs | Adjustment
Revenue recognition
Increase (decrease) in operating income			$ 1,300				$ 700					(2,800)	(14,500)	1,300
Increase (decrease) in net income			$ 900				$ 500					$ (1,600)	$ (8,000)	$ 3,500
Increase (decrease) in net income per common share (in dollars per share) | $ / shares			$ 0.03				$ 0.02					$ (0.06)	$ (0.30)	$ 0.13